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Form I
1: INTRODUCTION TO PHYSICS. Physics is the branch of science which deals with the study of matter in relation to energy. -Is the ability of doing work. Energy -Is The word physics comes from Greek word ‘physicos’ which which means Natural. Therefore Therefor e generally physics can be described described as the study of nature nature whose aim is to understand understand the behavior behavior of the the universe. Physics as a subject uses concept like force to explain different phenomena. force,, ener ner g y, mass, mass, wei wei g ht to A person who studies physics is called a phy or phy physicist sicist or physicia sician. n. RELATIONSHIP BETWEEN PHYSICS AND OTHER SUBJECT Physics is said to be the most fundamental of the natural science therefore the following are the subjects in which physics related to ;
Chemistry Biology Mathe Mathem matics Astrono Astronom my Geography APPLICATION OF PHYSICS IN REAL LIFE The following are areas/fields in which physics can be applied; AT HOME All tools and machinery that are used in our home to simply our works are made in accordance with the laws of physics .e.g .e.g hamm hammer , door door handles, handles, hing hi nge es, car j ack , pulleys etc. etc. MEDICAL FIELD. A variety of medical processes and machinery rely on physics .eg x-ra x-r ay, ult ultraso rasound und, syri syri nges nges and needles. SOURCE OF ENERGY some process and machines help us to obtain energy for our daily use.eg batte batterr i es ,ge ,g enerator nerator s and dynamo. TRANSPORT. Application of the laws of physics such us frict fr iction ion and frict fr iction iona al force force ensures that human being and animal can walk, run and stop without falling over. Vessels used in transportation such as car car s/aut s/autom omob obii les, ships, shi ps, aer aer o planes and trains are also able to move, brake stop where necessary. COMMUNICATION Example of devices that are used in communication are such as telephones, mobile p mobile pho hone ness, modem, television, transm tr ansmii tter tter r ecei cei ver ver , satelli satellite te dish ,new , newspa spape perr , ema emai ls, fax, f ax, short message message ser ser vice vi ce ( sms) sms) are due to knowledge acquired from physics. ENTERTAIMENT Physics enable people to enjoy a variety of leisure activities as evident in pho phottogra gr aphs, hs, D igita ig itall applianc liance es, exer cise ci se mac machi hine ness and other sports equipments such as inflated balloons, merry – go go- round roundss are used to entertain children. Music for example is recorded on tapes, CD using the skills acquired in physics . Television VCD ,DVD etc. INDUSTRY Physics have been able to came up with tools and processes that have resulted in advanced technological equipments and new discoveries Eg com compute puter s, binoc binocular ularss and telescopes. IN SCHOOL The instruments and apparatus used in school laboratory are made through application of the knowledge and skill acquired in physics class.
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IMPORTANCE OF STUDYING STUDYING PHYSICS PHYSICS 1.It help us to answer many questions about nature. 2.It enable people to acquire professions . 3.It imparts knowledge that is applied in designing and manufacturing different items which are useful in our daily life. 4.Physics is fun.
2: INTRODUCTION TO LABORATORY PRACTICE. . is a special room where scientific experiment are done . Laboratory is Appa Apparatus ratus-these are special tools and instruments which are used in physics laboratory. LABORATORY RULES AND SAFETY. As in all types of activities safety in handling of chemical, apparatus and equipment in the laboratory is the responsibility responsibility of every laboratory user. These is a set of rules should be observed when carrying out experiment in the laboratory. These rules ensure your safety, that of others that around you and the safety of the apparatus under use. RULES IN PHYSICS LABORATORY. The following are the rules to be observed when using in the laboratory. 1.Don’t enter in the laboratory without permission. 2.Don’t eat, drink, run and smoke in the lab oratory. 3.Follow instructions given before conducting an experiment. 4.Don’t topuch any electrical equipment with wet hand. 5.Don’t spill any liquid on the floor. 6.Never fight or quarrel in the laboratory . 7.Never use broken apparatus. 8.Perform the intended experiment . SAFETY MEASURES IN PHYSICS LABORATORY The following is a list of vital safety measures in the laboratory i.A physics laboratory should be well ventilated and its doors should open outwards. ii.Fire extinguishers should be fitted in accessible position. iii.Laboratory iii.Laboratory floor should not be polished as this will make them slipperly. iv.An adequately equiped first aid kit should be in every laboratory. v.Cabinets and drawers should be included in the design of a laboratory so as to be used for storing apparatus FIRST AID . F ir st aid is is the help which is given to a sick or injured person before taking him or her to hospital. IMPORTANCE OF FIRST AID
1.I t help help to pr eser ser ve lif li f e. 2.I t preve revents nts the victim ictimss cond conditio ition n fro fr om becom coming wo worse. rse. 3.I t sho shortens rtens reco recovery time ime. 4.I t pr pr events vents infe inf ecti cti on. on. 5.I t help helpss to reduc reduce e pains and suffe sufferi ri ng 6.I t br br i ngs hope hope to a vi vi ctim 7.I t pr pr events vents per per manent anent disabili ty Education is an ope n sesame to success”
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8.I t br br i ngs hope hope to a victim victi m. THE FIRST AID KIT is the small box which contains items and tool needed for first aid. F ir st aid kit is COMPONENT OF FIRST AID KIT. ITEMS/COMPONENTS
USES
Antisep Antiseptic soa soap
Washing hands ,wounds, and equipments.
Antisep Antiseptic solut solution ion
Cleaning fresh cut and bruises.
Assorte Assorted d banda ndages ges and cot cotton wool
Covering and drying wounds
D i sposab sposable le ster ster i le gloves gloves
Preventing direct contact contact with with victim’s victim’s body body fluids.
Liniment
Reducing muscle pains. pains.
Pain ki llers llers
Reducing pain pain
Adhe Adhesive banda ndage or pla plast ste er Thermometer
Covering minor wounds. To measure body temperature
Steri Steri le gauz gauze e
Covering wounds to protect them from dust and germs
Safe Safetty pins clips clips and tape.
Sucuring bandage or dressings
Scissors Scissors and razo razor bla blad de
Cutting dressing materials
P etrole troleum um jelly
Smoothening and soothing skin.
CAUSES OF ACCIDENTS IN THE LABORATORY.
i .Sli .S lip pper ly floor floor s. i i .I ncor ncor r ect use and hand handliling ng of apparat pparatus. us. i i i .G as leakages leakages fr om faulty gas tap taps. s. iv.Fires. v.Failure to follow the right experimental procedures procedures and laid down safety rules. SOME COMMON ACCIDENTS ACCIDENTS THAT MAY OCCUR OCCUR IN PHYSICS LABORATORY LABORATORY.
i .E lect lectriri c shock shock ii.Cut iv.Fainting v.Fire FIRE Fire is a chemical reaction that involves F uel, uel, heat heat and oxygen all combined together in suitable proportion hence producing fire fi re flam flame, smo smoke and heat
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Fire is the one of the most highty destructive accidents in the laboratory. Generally for fire to break out three factors must be fulfilled; .1H eat
2.Fue 2.F uell 3.Oxyge 3.Oxygen n In any physics laboratory fire may be caused by;
1.E lect lectrr i cal cal faults faults 2.Smo 2.Smoking ma materi als 3.Carel 3.Carele essne ssness ss 4.I g norance and negl neglii gence BASIC PRINCIPLE PRINCIPLE OF PREVENTING FIRE
1.No 1.N o light lig htii ng of ope open fi r es nea near buildings uilding s 2.No smo smoking ki ng in proh prohibit ibite ed area 3.No interf interfe erence rence with elec lectri cal cal insta installat llation 4.A ll electr lectrii cal cal appli appliance ancess must be turne tur ned d off i mmediately diately afte afterr use or or bef before leavi leaving ng the laboratory 5.All flam flammable sub substa stance nce sho should be locke locked d up in drawe rawer or or ca cabinet inet FIRE EXTINGUISHER Fire are classified according to the type of medium that is burning There are four (4) types of fire extinguisher
Water Dry powder F oam oam C ar bon bon dioxid dioxi de CLASSES OF FIRE
FIRE CLASS
Class A Class B Class C Class D Class E
BURNING MATERIAN Organic solid eg .wood, .wood, paper, plastic plastic wood Flammable liquid and greases eg petrol, eg petrol, kerosene kerosene paraffin, diesel diesel and alcohol Flammable gases eg. methane Combustible metal eg. magnesium or magnesium or sodium sodium Electrical appliances eg. damaged electrical damaged electrical cables
MOST APPROPRIATE FIRE EXTINGUISHER water Dry powder
Dry powder Dry powder Carbon dioxide
CHEMICAL WARNING SIGNS These are signs which must be obeyed in order to avoid accidents. For example toxic harmful, harmful, irritant,flammable, oxidizing agent, corrosive and explosive
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Form I TOXIC
This is the substance which is dangerous and cause death. HAMFUL OR IRRITANT
This is a substance which can affect our health. FLAMMABLE
This is the substance which can catch fire easily. OXIDIZING AGENT
This is a substance which speeds up rate of burning. CORROSIVE
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This is substance which can corrode surfaces and burn your skin. EXPLOSIVE
This is a substance which may explode easily. BASIC PRINCIPLE OF SCIENTIFIC INVESTIGATIONS INVESTIGATIONS is a set of techniques used by scientists to investigate a problem or answer questions. Scient Scientifific ic method hod is STEPS OF SCIENTIFIC S CIENTIFIC INVESTIGATION The following are steps follows when copying out a scientific investigation. 1. PROBLEM IDENTIFICATION This is first step in the scientific method it is when one makes a puzzling observation. An example of such as observation would be the mass of the bob of a perpendicular affects the time it takes to make one complete swing (isolation) 2. ASKING QUESTION A physicist asks a specific question based on what he or she has observe and wants to learn more about in example does the mass of the bob of perpendicular affect the hire it takes to make one complete swing? 3 FORMULATING A TESTABLE HYPOTHES A hypothesis is an intelligent gives gives that times to explain an observation it is suggestion of the answer to the answer to the question asked for example the mass of the bob of the pendulum affects the time it takes to make one complete swing 4. PERFORMING EXPERIMENT Is a test under control condition is used to determine whether the formulated hypothesis hypothesis true or false. There three different various these are;
i . D epende pendent nt vari able able i i . I ndepe ndepende ndent nt var var i able. able. i i . C ontrolled ntrolled va var i able. ble. 5 DATA COLLECTION AND ANALYSIS Data collection involve recording what has been observed during the experiment. Data collection helps in drawing conclusion. Example
Mass of bob g Time for one swing 10 2 20 2 30 2 40 2 6. DATA INTERPRETATION We look a possible tone or pattern and explain it 7. DATA PRESENTATION Education is an ope n sesame to success”
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Data presentation involves the use of mathematical concept to represent the data or results collected this could include the use of pie chart, graphs and formulate 8. DRAWING CONCLUSION Conclusion .is the summary of the result of the experiment
3: MEASUREMENTS. MEASUREMENTS. Measu Measure rem ment is the process of assigning numbers to observation or events Measurement should have two parts
1. Numb N umbe er par par t 2.Unit part E.g. 2kg,5s physica sicall quant uantitie itiess A complete measurement is called phy BASIC FUNDAMENTAL QUANTITIES There are two categories of physical quantities which are; I . F undam undamental ntal quantiti uantitie es I I . Derive Deri ved d quant uantii ties ties fundamental quantities of nature include;
1.Length 2.Mass 2.Mass 3.tim 3.time e 4.Temperature 5.Amo 5.Amount unt of sub substa stance nce 6.elect 6.electrr i c curre curr ent 7.Luminous intensity N.B: Mass, Mass, L ength ngth and Time Time (ML (M L T) are known as the basic physical quantities of measurement THE FUNDAMENTAL QUNTITIES AND THEIR UNITS QUANTITY
SI UNIT UNIT SYMBOL Metre lenght m kilogram mass kg second time s kelvin Temperature k Amount Amount of sub subst sta ance nce mole mol ampere E lect lectrr i c curr curr ent A candela Luminous intensity cd
1. LENGTH Length is the distance between two points. This is the commonly made measurement in our daily life. The S.I unit of Le unit of L ength is metre (m) The length of object or distances tend to vary for example distance from the earth to the sun and diameter of a wire. To cope with this great difference, there are other several units obtained from metre such as kilometre,
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centimetr centimetr e ,mill ,mi llII metre, mi mi crom cr ome etre tr e and nanomet nanometrr e. Their equivalence are as follows; 1km — 1000 1000 m 1m — 100 100 cm 1m — 10 106 µm
1m---109 nm E xample amples. s. 1.Change the 0.01km into centimeters.
Solut Solution ion:: 1km = 1000000cm 0.01km = cm?
1000000×0. 0 1 1 = 1000cm
APPROPRIATE MEASURING INSTRUMENTS. 1.LENGTH The instruments commonly used in the laboratory to measure length include, M etre ruler ruler i. Me
i i .Ve .V er nier nier callipe calliperr i i i .Mi .M i crome crometre scr scr ew gauge iv.Tape measure I.USING METRE RULER In an elementary physics laboratory the metre and half metre ruleR are normally used. These are mainly wooden and graduated in centimetres and millimeters
metre rule When taking measurement always ensure that your eye is right above the mark one the scale of the metre rule, otherwise the value will have an error . The error is due to parallax Parallax occur when a point an object is viewed from different positions. This makes the object to shift positions is the apparent motion of an object relative to another when the position of the eye is varied Parallax is
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II.USING VERNIER CALIPER V er nie ni er cali calip per is an instrument used to measure the length of an object to an accuracy of 0.01cm. A vernier calliper has two major scales;
i .Ma .M ai n scale scale ii.Vernier scale
READING THE VERNIER CALIPER 1. The base measurement is read on the main beam from left to right of the (0) on the main beam scale read the main scale. Use the vernier zero (0) as the focus 2.Look at the graduation on the vernier scale to see which line up exactly with one of the main scale then read the number on the vernier scale not the main scale. 3. Add these two readings together then check the reading. 4. The total is the measurement of the vernier caliper. Examples: Find the readings of the following vernier calipers below;
1.
.
solution: Main scale= 0.00 cm Vernier scale=0.06 cm Reading of the vernier caliper = Main scale + Vernier scale = 0.00 cm + 0.06 cm
= 0.06cm 2.
solution: Main scale=8.6 cm Vernier scale=0.02 cm Reading of the vernier caliper = Main scale + Vernier scale = 8.6 cm + 0.02 cm
= 8.62cm|
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Form I
III. USING MICROPMETER SCREW GAUGE Mi crome rometer scre screw w gauge gauge is an instrument used to measure the length of an object to an accuracy of 0.001cm /0.01mm For this reason it is used to measure the length of objects with smaller diameters such as diameter of wires and ball ball bear i ng. ng . The micrometer screw gauge has two scale which are;
1. T he main main scale 2. The thimb himble sca scale
READING THE VERNIER CALIPER Readings on the microscope are taken as follows; The reading of the micrometer screw gauge is the sum of the main scale reading and the thimble scale reading. Examples: Find the readings of the following micrometer screw gauge below
1. solution: Main scale=2.5 mm Thimble scale scale=0.38 mm Reading of the vernier caliper = Main scale + Thimble scale = 2.5 mm + 0.38 mm
= 2.88 mm 2. MASS Mass Mass is the quantity of matter in an object. The S.I Unit of ilogra am (K g) of mass is K ilogr The apparatus commonly used to measure mass of objects in the laboratory are;
i .B eam eam balance balance
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i i . Di D i gi tal tal balance balance /electr lectr onic onic bala balance nce
B eam balance balance
D i gi tal tal balance balance
3. TIME of time is Seco Time is the interval between one event and another. The S.I unit of Second nd (s) Time can be measured by using;
i . Stop top wat watch ch i i . Wri Wr i st watc watch h ii i. Clo C lock ck
Stop Stop watch
Wri st watch
Clock Clock
DERIVED QUANTITIES D er i ved ved quantiti quantitie es are obtained by combining two or more of the fundamental quantities through multiplication or division. Ar ea, Volum Volume, Density Density,, Velo Velocity, city, We Weig ight ht and Work. Example of derived quantities are Are QUANTITY
SI UNIT UNIT SYMBOL Square metre Ar ea M 2 Cubic metre Volume M 3 Newton Weight N Joules Work J Metre per per second Velocity M/S VOLUME Volume is the quantity of space that an object occupies . The S.I unit unit of of volume is cubic metre (m 3 ) other unit of volume includes; i.Cubic centimetre (cm3 )
ii .Mi llilitre (ml) (ml) iii .Litre (L ) Solid, L iquid iquid or The technique for measuring volume vary depending on whether the sample is a Solid, or Gas I.SOLID A.DETERMINING THE VOLUME OF REGULAR OBJECTS Education is an ope n sesame to success”
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Form I
If the solid have regular shape such as cube ,cylinder or sphe sphere re its dimensions are measured and the appropriate formula is used to calculate the volume.
1. VOLUME VOLUME OF CYLI NDE R
2. VOLUME VOLUME OF CUBE
2. V OLUME OLU ME OF CUB C UB E
EXERCISE
1. Calculate the volume of rectangular block of sides 15cm ,8cm and 7cm . 2. Calculate the volume of cylinder with the height of 14cm and diameter of 20cm. 3.Calculate the volume of sphere with a diameter of 28m. 4.A cylinder with a height of 100cm has a volume of 61600m 3 calculate its diameter. B: DETERMING THE VOLUME OF IRREGULAR OBJECTS If the solids has an irregular shape such as a stone ,it is submerged /immersed in a measuring cylinder containing water ,then the volume of displaced water taken as the volume of the solid . Measuring the volume of an irregularly shaped solid object is based on the principle that, when an object is completely submerged in water it displaces a volume of water equal to its own volume. displacement ent or mer sion si on met method. hod. This is known a displacem or i mmer Volume of irregular object can be measured by using;
i . A g r aduate duated d cyli cylinde nderr i i . E ure ur eka can can or or over ver flow can can Education is an ope n sesame to success”
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Form I
I. USING GRADUATED CYLINDER Suppose you wanted to measure the volume of are small stone . The following stapes are necessary; 1. Fill the graduated cylinder with about 30cm 3 of water 2.Careful measure the i nitial ni tial volum volume e of water [V ] 1] 3.Then lower the stone into the water 4.Measure the fina fi nall volum lume of water [V 2 2] ] 5.The difference between the F i nal nal and and I nitial volumes gives the volume of the stone [V s ] s
V s= F i nal volum volume e-i nitial ni tial volum volume e
V s= F i nal volum volume e-i nitial ni tial volum volume e V s= V 2 - V 1 V s = 40cm 3- 30cm 30cm 3 = 10 cm 3 Therefore the volume of the stone is 10 cm 3 II. USING OVERFLOW CAN / EUREKA CAN If the object is too large to fit into the graduated cylinder an alternative method is to use eureka can commonly known as overflow can STEPS 1.Fill the eureka can with water up to the level of spout 2.Tie the irregular solid [stone] with string 3.Gently lower a stone into the water by using a string 4.The stone will displace some water which will be collected in the beaker 5.Transfer the displaced water into a graduated cylinder 6.Measure the volume of water 7.This is the volume of the solid
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II. LIQUID The litre is the standard unit used for measuring volume of liquids
1litre=1000cm 3 = 1000ml This implies that 1cm 1cm 3 =1ml Instruments used for measuring volume of liquids in the laboratory are;
i.Beakers i i .Ca .C alib li br ated ted flasks iii.Burette iv.pipette v.Me v.M easuri ng cyli cylind nde er
B eaker aker
C onical fla fl ask
B ure ur ette tte
P i pette tte
M easuri sur i ng cylinder cylinder
III. GAS A gas always fill any container in which it is placed therefore the volume of the Gas can be determined by measuring the volume of the container. ERRORS Errors is a minimal deviation from true volume Is a measure of estimated difference between observed and the value of a quantity that is being measured SOURCES OF ERRORS
i .F ault duri duri ng manufactu nufacturr e i i .Da .D amage duri duri ng use iii.Poor storage i v.H uma uman fa f actor ctor
TYPES OF ERRORS
i. Parallax i i . Zero Zero er er ror i i i . H uma uman facto factor r DENSITY is the mass of an object per unit volume. Density is
=
unit of logr am per per cubi cubi c me metre (kg (k g /m 3 ) The S.I unit of density is K i logra gr ams per cub cubic ic cent centim ime etres (g/ (g /cm 3 ) and gra gr ams per millili millilittres Other units used for measuring measuring density are gra
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(g/ml) DENSITIES OF SOME COMMON SUBSTANCES SUBSTANCE
Alumini Aluminium um Copper Gold Lead Water I ce E xamp xample; le;
DENSTIY(g/cm3)
2.7 8.3 19.3 11.3 1 0.92
1.What is the density of a piece of wood of mass 25g and volume of 29.4cm 3? Solution Data given Mass =25g Volume =29.4cm3 Density =?
= = .
The density of a piece of wood is 0.9g/cm 3 2.A cup of gold colored metal beads was measured to have a mass of 425g by water displacement the volume of the beads was calculated to be 48.0cm 3 identify the density of the metal . Solution Data given Mass =425g Volume=48.0cm 3 Density=?
= = The density of metal metal is 8.8542 g/ g /cm 3 3.Calculate the density of block of glass of mass 5.4g and volume of 2cm 3 Solution Data given: Mass=5.4g Volume=2cm 3 Density=? But
=
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Form I
= . The density of block is 2.7g/ 2.7g/ccm 3 DENSITY OF REGULAR SOLID
The density of regular solid can be obtained by calculation once its mass and volume have been measured It is found by dividing mass and volume. The mass of the material can be obtained by using beam balance on the other hand volume can be obtained by using various methods depending the nature of the material DENSITY OF IRREGULAR SOLID Density of irregular solid can be obtained by; Measuring its mass by using beam balance or digital balance Determining its volume through displacement or immersion method involving the Eureka or measuring cylinder Divide the mass and the volume obtained
== Examples; 1. An irregular solid x has a mass of 50g when its totally immersed in water of volume 60cm 3 the final volume of water is read as 70cm 3 calculate the density of the irregular solid x.
Solut Solution ion Data given Mass of an object =50g =50g Initial volume volume f water water =60cm3 Final volume volume of water water =70cm3 Displaced water water = V 2-V 1 But
=
= 2 1 = 7050 60 50 = 103 5g/cm 3 Density of of the solid x is 5g/cm
DENSITIES OF INSOLUBLE GRANULES Determining the densities of insoluble small particles such as sand sand gra gr ains also possible they must be held is some type of container while being measured one technique involved is by using density bottle. A density bottle 50ml or 100ml. has a precisely measured volume, usually 50m The following are steps followed when using a density bottle to Measure the density of insoluble granules eg
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Form I
sand. 1. Measure the mass of an empty density bottle with its stopper record as ( m 1) 2. Add a small amount of sand to the bottle, replace the stopper and measure (m 2) 3. Fill the bottle with water and measure as (m 3) 4. Since the density of water is 1g/cm 3,the volume of water is cm 3added to the bottle is numerically equal to the mass of water in grams Volume of water in cm3=mass of water in grams Volume of sand=volume of bottle=volume of water 5.Calculate the density of sand by dividing its mass by its volume
() = () Examples
DENSITY OF LIQUIDS The density of liquid can also be calculated if its mass and its volume are known. the Density of a liquid can be determined determined through the following steps;
1) 1. Measure the mass of an empty beaker (m ) ) 2.Run known volume of liquid into the beaker and record the mass as (m 2 ) 1)g 3. Substract m1 from m2 to get the mass of the liquid (m 2-m )g 4.Calculate the density of the liquid by dividing mass obtained by the volume of liquid
= m) = ( m()
Examples; In an experiment to determine the density of liquid Y, Chidibo a form1 Student obtained the following results Mass of empty beaker=500g Mass of beaker + liquid (25cm3) =600g What did he obtained as the density of liquid Y, Data given;’ given;’ Mass empty beaker=500g Mass of beaker and liquid=600g Volume=25cm3
== ( 2 m1m1)) == m2m () 6 00 500) 50 0) == (600 (25)
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=
The density of liquid Y is 4g/cm 3
RELATIVE DENSITY (R.D) Relative density is the ratio of the density of substance substance to the density of water
=
Relative density has no unit. Therefore relative density is unitless. Examples; 1.An object has a density of 7g/cm 3 calculate relative density. Data given Density=7g/cm3 Density of water=1g/cm3
= = .= 7/ 1/
Relative density of an object is 7 DETERMINATION OF RELATIVE DENSITY OF LIQUID Relative density of liquid can be determined by using relative density bottle
PROCEDURES. 0) 1. Find the mass of an empty bottle (m ) 2.Find the mass of bottle=liquid bottle=liquid (m ) 1) 3. Find the mass of bottle with water (m 2 ) )
= = ( ())
Examples: 1. In an experiment to determine the relative density of liquid X Samba a form1 Physics student attained the following results. Mass of an empty relative density bottle=15g Mass of bottle liquid X=35g Mass of bottle water=40 Calculate density of liquid X Data given Mass of bottle=15g Mass of bottle liquid=35g Density of liquid=?
= = ( ()) Education is an ope n sesame to success”
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Form I
= ( )) .= ()
=
Density of liquid= 0.8g/cm 3 APPLICATION OF DENSITY AND RELATIVE DENSITY IN EVERYDAY LIFE
R elative density density and density density has its i ts app applilica catition on in in our ever ver yday yday live li ves. s. Thi T hiss include i ncludess 1. De D esigni si gni ng shi ps and planes lanes 2.Det 2.Detemining ini ng densitie nsitiess of unkno unknow wn liquid liquidss 3.To determine rmine mineral ineral /cont conte ent of rocks rocks ( geo geologi logist stss and mineral ineralo ogist gi sts) s) 4.it 4.i t help helpss in i n ide i dentif ntifying ying mater ter i als 5.Sele 5.Select ction ion of build building ing ma materi als 6. De D esigni si gni ng swim swi mmi ng and and di di ving equipme quipments IMPORTANCE OF MEASUMENTS.
1. Architecture and engineering 2 I n trade rade 3.I n agricul gr icultture 4.I n hospi hospi tal tal 5. I n fash fashion ion indus industtri es. 6. I n schoo schools. 7. I n transp transpor t industry industry
1. What is the density of piece of wood of mass 25g and volume of 29.4 cm 3. 2. A cup of gold colored metal beads was measured to have a mass of 425g, by water displacement the volume of the beads was calculated to be 48.0 cm 3. Identify the volume of the metal. 3. Farhan threw a plastic ball in the pool for his dog to fetch. The mass of the ball was 125g. What must the volume be to have a density of 0.500g/ cm 3 ? 4.What is the mass of cylinder of lead that is 2.80 cm in diameter and 10cm 1 0cm in height. If the density of the lead is 11.4g/cm 3. 5. The volume of the solution was measured in a graduated cylinder was 45 cm 3, if the mass of solution measured to be 60.75 grams. What is the density of the solution? 6. An ice cube measured 58cm by 58cm by 58 cm has a density of 0.917g/ cm 3 , what is mass? Education is an ope n sesame to success”
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7. Gasoline is a non polar liquid that will float on water 450g o f gasoline is spilled in puddle of water. If the density of gasoline is 0.665 g/cm3. 8. The density of Aluminium Aluminium is 2.70 2.70 g/cm3. If the mass of a piece piece of Aluminium is 244g. What What is the volume of Aluminium? 9. The density of substance is 1.63 1 .63 g/cm 3. What is the mass of 0.25 litres of the substance in grams. 10. A 10. A cup made of an alloy of Gold and Silver has a volume of 60 cm3 and a mass of 1050 g. Find the mass of Gold contained in the cup. (Density of Gold = 19.3 g/cm3, Density of Silver = 10.5 g/cm3)
3: FORCE. Force is a pull or push of a body. Force can; The S.I unit of force is the Newton (N) The branch of physics that deals with the effect of force on matter is called mechanics. Force can;
C ause a movi moving ng body body to stop, stop, A bo body at rest rest to sta start moving. Change the size and shape of an object force can. Affe Af fecct dir ection ction and the spe speed of a moving bo body . TYPES OF FORCES There are four types of fundamental fundamental forces which are GRAVITATIONAL FORCE 1.GRAVITATIONAL Is the force of attraction between between bodies in the universe. universe. A n example is the earth’s gravity which pulls objects towards earth’s centre.
The force of gravity is always equal to the weight of the object. This can be stated as;
= = = = From ;
but
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= Examples; 1. If an object has a mass of 60 kg how much would it weight on earth? Solution: Data given: Mass=60kg Acceleration due to gravity g=10m/s 2 Weight=? From;
= = F=60kg x 10m/s2 F = 600N
2. If an object weight 30N on the earth what is its mass Solution Data given Force = 30N g=10m/s2
ℎ = / = = 30 10 Mass of an object is 3kg
PROPERTIES OF GRAVITATIONAL FORCE i. It is always attractive ii. It is weakest force among the four basic forces iii. It is central force iv. It operates over very long distance 2. STRONG FORCES. These are forces responsible for binding nuclei of an atom they hold the nucleus together (neutron and proton) 3.WEAK FORCE Is the force responsible for various trends of radioactive decay. The decay of fundamental particles such as Beta particles. 4. ELECTROMAGNETIC FORCE Is the force which cause magnetic and and electric effect effect PROPERTIES OF ELECTROMAGNETIC i. It may be repulsive or attractive ii. It is a central force iii. It is stronger than gravitational force iv. It is also long range force
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EFFECT OF FORCE Force have several effects effects an object in real situation these effects include Friction, Stret Stretching, ching, Com Compress ression ion,,
r esto stor i ng, A ttr ttr acti cti on , R epulsion, Torsi on, Vi V i scosity, scosity, Ai A i r r esistance sistance 1.FRICTIONAL 1.FRICTIONAL FORCE Friction is the force that one surface an object encounter when resting or moving over another .When one object slides over another object friction tries to stop movement, thus friction is an oppo opposi sing ng f or ce.
shoe sole soless Friction force produces heat and causes wearing and tearing of car tyres and sho 2. STRETCHING FORCE This is the force that passes through a strong cable, loop or wire when it is pulled tight by force acting from both ends.
3. COMPRESSIONAL AND RESTORING Compressional force is force which when we applied to an object it result into a decrease in its volume. R esto stori ng force is the force which returns the object to their original shape and size.
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4. AIR RESISTANCE Ai r resist resista ance nce .is the force that resist the movement of an object through the air.
5. VISCOUS FORCE is the resistance of the fluid to flow; example of viscous fluids are honey, grease, and turpentine Viscosity is
6. ATTRACTIVE AND REPULSIVE FORCE Attrac Attracttive force force is the force by which one object attract another. E.g a magnet exert attractive force an a piece of metal or (ir on fillings) Attrac Attracttive force force occurs when unlike poles of the magnet are brought together. R epulsive force for ce is the force of separation that a body or particle exerts on another NB: like poles r epel epel, unlike poles attract each each other
7. NORMAL FORCE This is support force exerted upon an object which in contact with another stable object.eg when a person leans
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against the wall the wall supports the person by pushing horizontally
8. APPLIED FORCE If you push a box containing containing books across a floor then there is a force acting on the box is known applied force
9. TORSIONAL FORCE This is a force produce on solid object when it is twisted.
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5. ARCHIMEDES PRINCIPLE AND THE LAW OF FLOATATION CONCEPT OF UPTHRUST Consider a cork that is hold just below the surface of liquid and then released. The cork comes to surface immediately.
This show that while inside the liquid an upward force (upthrust) acts on a cork. This force is greater than the weight of the cork hence a cork is pushed to the surface. BUOYANT FORCE B uoyant uoyant f or ce is a upward force that acts on an object if partially immersed immersed in a fluid (liquid or gas) This upward force enables the object to float or at least seem lighter. You would not be able to swim in water if it were not for an upthrust force to act on your body .Water vessels ships and boats sail on water due to this force, otherwise they would sink. like ships
RELATIONSHIP BETWEEN APPARENT AND REAL WEIGHT When the body is totally or partially immersed in the fluid the buoyant force on the body is equal to the weight of the displaced water or fluid submerged bodies always weight less than when not immersed in the fluid. This loss of weight when a body bod y is totally or partially immersed in the fluid is not real hence it is apparr ent loss in i n wei wei g ht . known as appa Ap A pparent rent weight ig ht is the weight of the body when is totally or partially immersed in the fluid. is the weight of the object in air. R eal we wei g ht is Ap A pparent rent loss loss in weight is the loss in weight when the body is totally or partially immersed in the fluid. Therefore;
= =
ARCHIMEDES PRINCIPLE If an object is immersed in a beaker full of water, it displaces some of the water. A Greek scientist by the name Ar chim chime edes discovered that there was a relationship between upthrust acting on the body and the weight of the liquid displaced, this relation is known as Archimedes principle. “ If an object object is partially partially or totally totally immersed immersed in the fluid it experienc experiences es an Ar chim chime edes pri ncipl nciple es sta states that hat , “ If upthrust which is equal to the weight of the fluid displaced .” displaced .”
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= =
Examples: 1. When an object is totally immersed in water, its weight recorded as 3.1N. If its weight in air is 4.9N, calculate the upthrust acting on the object. Solution; Data given: Weight in air = 4.9N Apparent weight = 3.1N Upthrust = ?
ℎ ℎ ℎ = = ℎ ℎ ℎ ℎ ℎ== 4.9 9 3.1
= 1.8N The upthrust acting on the body is 1.8N 1. A body immersed in water displaced 1.1N of the liquid. If its weight while in water is 3.3N. Find its weight in air. Solution; Data given: Water displaced = 1.1N Apparent weight = 3.3N Real weight = ?
ℎ ℎ = = ℎ ℎ ℎ ℎ ℎ ℎ= = ℎ ℎ + + ℎ ℎ ℎ= ℎ = 3.3+ 3 + 1.11
= 4.4N The weight of the object in air is 4.4N DETERMINATION OF RELATIVE DENSITY Relative density of a substance can be expressed as;
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= =
In terms of apparent weight weight loss it can be expressed expressed as ;
Relative density of substance ( Both solids and liquids) can be therefore obtained by applying the Archimede’s principle. 1. The weight of the stone in air is 25N and 17N in water, calculate the relative density. Solution; Data given: Weight of stone in air = 25N Weight of stone in water = 17N Relative density= ?
== ℎ ℎℎ 25 == 2517 .=
= 3.125 3.125 Therefore the relative density is 3.125 Archimedes principle can be used to determine the relative density of both solids and liquids. Previously we learnt that;
= = = == = ( () = ( () ( () = ( () And for liquids;
NOTE: The relative density of an object
BUT;
Therefore;
BUT;
ALSO;
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= = = Therefore;
NOTE: The relative density also determines the proportion of a floating body that will be submerged in a fuid. If the body is 70% 70% as dense as the fluid, 70% 70% of its volume will be submerged. Examples: 1. In an experiment to determine the relative density of a liquid, a solid weighed as follows; Weight in air, WO = 8.6N Weight in water, W1 = 6.4N Weight in liquid, W2 = 5.4 N Calculate the relative density of the liquid Solution;
Data given: Weight in air, WO = 8.6N Weight in water, W1 = 6.4N Weight in liquid, W1 = 5.4 N Relative density of the liquid= ?
=.WW−.−W−W
.−. 1.2
=
=1.2
Relative density of the liquid=
SINKING AND FLOATING SINKING Sinking Si nking is the tendency of an object to drop or to fall to the lower levels of the fluid. FLOATING F loa loati ng is the tendency of an object to remain on the surface of the fluid due to the forces exerted by the fluid. is the ability of an object to float. Examples of an object that can float include s hips, hips, canoes, canoes, boats Buoyancy is and balloons. balloons. CONDITIONS FOR FLOATING The following are some of the conditions to be satisfied before a body can float; 1. The object’s submerged volume must be enough so as to displace a lot of fluid. 2. The density of the object must must be less than the density of the surrounding fluid. 3. The upthrust due to the liquid must be equal to the total weight of the object. RELATIONSHIP BETWEEN UPTHRUST AND FLOATATION
= = = = = = . = Since;
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Therefore for an object to float its apparent weight must be ZE R O. LAW OF FLOATATION The floatation floatation law states that, “ The floa fl oatiting ng body body displaces displaces its i ts own own we wei g ht of of the flui flui d i n which i t floats floats ” If an object flats;
= = %
LAW OF FLOATATION IN EVERYDAY LIFE There are many objects and vessels that floats or can be made to float, since they apply the law of floatation in their functioning. Examples of those objects are Balloons, are Balloons, Ships, Ships, Canoe, Canoe, Hot air Balloons and Balloons and Submarines. HYDROMETER H ydrome ydrometer ter is an instrument used for determining the relative densities of liquids. It is usually made of glass consisting of a cylindrical stem which is graduated and glass bulb at its end. The graduation at the stem of the cylinder start with small number at the top and end with large number at the bottom, thus thus it sinks more in less less dense liquids.
1. An object is hung from a spring balance its weight is 40N in air and 30N when immersed in water; (a) Calculate upthrust of the object (b) Calculate the weight of the fluid displaced (c) What is the mass of displaced water Education is an ope n sesame to success”
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(d) What is the mass of displaced water (e) What is the volume and mass of the object (f) Calculate relative density (g) Calculate its density 2. A hot air balloon including the envelope, gondola burner, fuel and one passenger has a total mass of 450kg. If the air outside the balloon is at 20C and has density of 1.29 kg/m 3, air inside the envelope heated to a temperature temperature of 120C which has a density density of 0.90 kg/m 3. What volume must the envelope expand to just lift the balloon into in to the air? 3. An object has mass of 150g and a volume of 200 cm 3. If placed in water, how much of its volume will be submerged? 4.A weather balloon using Helium of density 0.178 kg/m3 requires a volume of 250 m3 to lift its payload. If Hydrogen gas of density0.090 kg/m3 were used instead what would be the required volume? 5. Icebergs are hazardous to shipping because so much of their volume is below the water level. If the density of the sea water is 1025 kg/m3 and the density of the ice is 909 kg/m 3. What percent of an iceberg is below the water level?
6. STRUCTURE AND PROPERTIES OF MATTER is anything which has got weight/mass and occupies space. Matter is made up of thin particles called Matt Matter is atoms STATES OF MATTER Matter exist in three physical states which are;
i. Solid state i i .Li .L i quid sta state i i i .G ases ses state state I. SOLID STATE Solid state have definite shape and volume, particle in a solid are closed parked together therefore the particles are not free to move because they are held together by strong inter molecular forces. Examples of solids are; wood, stone, books, ice, rock, iron and pen . II. LIQUID STATE Unlike solid state, liquids have fixed volume but variable in shape .This largely because a liquid will assume the shape of any container in which it is hold. In liquids, the atoms and molecules are only slightly held together weaker than in solid. Examples of liquids are water, kerosene, milk, petrol, diesel, oil, honey, wine, saliva and urine III. GASES STATE Gases have neither a fixed shape fixed shape nor nor fixed volume .Gases always fill the container in which they are held. Atoms and molecules in gases are so far apart that they do not interact with each other, therefore gases have weakest intermolecular forces of attraction. Examples of gases are oxygen, are oxygen, hydrogen nitrogen, Sulphur dioxide and Carbon dioxide . THE PARTICULATE NATURE OF MATTER Matter is not continuous but is is made up of particles. This was proved by phenomena referred to as Brownian
motion. In 1927 , a scientist by the name R ober t B r own used a microscope and observed that pollen grains suspended in Education is an ope n sesame to success”
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water moved short distance in an irregular zig zig-z -za ag manner. Brownian motion states that ,” Matter ,” Matter is made up of tiny particles that are in state of continuous random motion.” KINETIC THEORY OF MATTER The kinetic theory of matter states that “all matter is made up very small particles that are in constant motion” . The more heat energy the particles posses the faster they move . The kinetic theory of matter is also known as the molecular theory of matter. 1. ELASTICITY E last lastii city is the ability of an object to regain its original shape and size after the removal of the deforming force. E lasti lasti c ma mater ter i al is the one which is able to regain its original shape and size after the removal of the deforming ubber band, band, catapult catapult e.t.c e.t.c force. Examples of elastic materials are r ubber RELATIONSHIP BETWEEN TENSION AND EXTENSION OF A LOADED ELASTIC MATERIAL; HOOKE’S LAW ‘‘ the extension of the spiral spring is directly proportional to the load provided that the Hooke’s law states that ‘‘the elastic limit is not exceeded.’’
APPLICATION OF ELESTICITY At home ; i. Rubber i. Rubber gaskets gaskets that seal refrigerator’s refrigerator’s doors ii.Clothing iii. Spring in furniture iv. Rubber band that holding things together v. Toys and balloons In transport; i. Rubber tyes . ii . Aeroplanes Aeroplanes wings. wings . In industries;
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i.Steel beams used in construction construction ii.Conveyor belts iii.Measuring weight iv.Insulation against vibrations and sounds 2. ADHESION AND COHESION I. COHESIVE FORCE C ohesi ohesive ve force for ce is the force of attraction between molecules of the same material. II.ADHESIVE FORCE Adhe Adhesive force force is the force of attraction between molecules of different materials. APPLICATION OF COHESIVE AND ADHESIVE FORCE 1.Sticking two different objects together by tape or glue (adhesive force) 2. Cohesion assists transport of water in plants and animals 3. Ink sticks on paper because of adhesive forces being greater than cohesive force. 3. SURFACE TENSION Surfa Surf ace tension nsion is the ability of the surface of the liquid to behave like a fully stretched skin. Cohesive forces are responsible the surface tension of liquids. Surface tensions enables objects such as small objects even metallic ones(needles, razor blade) and insects to float on the surface of water. When needles, papers, clips, razor blade and chalk powder were placed on the surface of the water they all float on tops, thus the surface tension of water was high. However, when detergents was added to the water, the same object sunk to the bottom of trough, this means that the introduction of detergents interfered with surface tension of the liquid therefore detergent decreased decreased the surface tension of water. Detergents are examples of Surfactant. Surfactant is a substance that reduces the surface tension of the liquid. NOTE: The term term Surfactant Surfactant is an acronym for Surf ace ace Active Agent FACTORS AFFECTING SURFACE TENSION The surface tension of any liquid is affected by the following factors; i. Nature of the liquid ii. Contamination of the impurities iii. Temperature APPLICATION OF SURFACE TENSION 1. The cleaning action of soap is due to ability to lower surface tension of water. 2. Mosquito normally lay eggs in water, the eggs hang on the water surface. When a small amount of oil is poured on water, water, it reduces reduces the surface tension, tension, this breaks the elastic film and the eggs are drowned and killed. 3. Surfactants are also used in emulsion of two liquid like oil and water, which normally do not mix. 4. Hot soup has lower surface tension than cold soup, as a result hot soup spreads over a large area of the tongue hence hot soup is testier than cold soup. 4. CAPILLARITY is the tendency of liquids to raise or fall in narrow tubes. Capillarity is
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APPLICATION OF CAPILLARITY 1. It facilitates the transport of water and nutrient in plants 2. It assists circulation of blood in animals. 3. It facilitates the movement of ground water. 4. It is the principle on which towels absorbs water. 5. The wick of the lamp draws up the fuel (kerosene) by using capillarity. 5. DIFFUSION Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. For example diffusion occurs; i. When a bad egg (rotten egg) is broken ii. When a bottle of perfume is sprayed 6. OSMOSIS Osmosis is the movement of water molecules from a region of lower concentration of solute to the region of higher concentration of solute through semi- permeable membrane.
7.
PRESSURE
a rea Pressure is the force acting normally per unit area
=
=
Therefore the S.I unit of pressure is N ewton wton per per M etre tre square square (N/M N/M 2 ) Other units of pressure are;
1Nm 2=1Pa 1atm=760 1atm=760 mmH mmHgg 1atm=1.01×10 5 N/M N/M 2 =1.01×10 5 Pa A. PRESSURE DUE TO SOLIDS Pressure due to solids depends on the surface of contact. A force F applied onto a small area exerts a higher pressure as applied onto onto a large large surface.
E xample amples; s; 1.Consider a block of wood that weigh 30N and measure 5m by 10m by 4m. If it is placed on a table with a largest possible area (10m × 5m) in contact with the table, it exerts less pressure that it would when exert when placed with with its smallest smallest possible possible area (5m × 4m) 4m) in contact with the table. table. (a) Large surface= (10m × 5m) Force= 30N Area= 10 × 5= 50m2
= = =
=0.6
Minimum pressure = 0.6 N/M 0.6 N/M 2 Education is an ope n sesame to success”
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(b) Small base area = (5m × 4m) Force= 30N Area= 5m× 4m= 20m2
= = =
=1.5
Maximum pressure = 1.5 N/M 1.5 N/M 2 2. The tip of a needle has a cross-sectional area of 1× 10 -6 m2. If adoctor applies a force of 20N to a syringe that is connected to a needle, what is a pressure exerted at the tip of the needle? Solution Force= 20N Area= 1×10-6 m2 Pressure=?
= = ×
Pressure =2×10 =2×107 N/M 2 APPLICATION OF PRESSURE DUE TO SOLIDS 1.Objects with sharp points. E.g nails, pins, spears, arrow heads. 2. Objects with sharp edges. E.g razor blade, blade, knife, knife, matchette 3. Buildings are constructed with wide foundations to ensure that the weight of building acts over a large area. 4. During construction of railway wide wooden sleepers are placed below the railway trucks. 5. Caterpillars and tractors tyres have wide surface area in order to significantly significantly produce low pressure. This prevents them them to sink in soft soil. 6. Heavy loads (cargo) are carried in trucks which have many many tyres. The presence of many tyres increases surface area in contact, hence reduced pressure on the roads. 7. Wide straps for school bags. If thin straps with small area were used, high pressure would be produced causing pain to the shoulders of the pupil. 8. Wide soled shoes are used on sand surface or snow to reduce pressure and avoid sinking. B. PRESSURE IN LIQUIDS A liquid will exert pressure on an immersed object as well as on the walls of the container. CHARACTERISTICS CHARACTERISTIC S OF PRESSURE P RESSURE IN LIQUID The pressure at any point in any liquid at rest depends on;
1. De D epth ( h) ρ ) 2. D ensity nsity of liqu liquid id ( ρ It does not depend on area;
=
But;
= =
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But;
But;
Form I
= = = = =ℎ/ h
= ==
Examples; 1. Calculate the pressure acted on a diver at a depth of 20m below the surface of water in a sea. Solution: Data given: Density= 1000Kg/m3 Height= 20m Acceleration Acceleration due to gravity = 10N/ Kg
=ℎ = 1000000 20 1010
= 200000N/M2 200000 00N/ N/M M 2 or or 2 x 10 5N/M N/M 2 Pressure exerted on a diver is 2000 The acceleration due to gravity( g) is constant. Therefore, pressure is proportion to desinty (P ρ) as well as depth (P ) of the liquid. This can be seen clearly when holes are made in a container at different
h
levels and the container is filled up with water. The speed or height of water jets coming out of each hole would be different.
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As the depth increases, water comes out with higher speed indicating greater pressure. This knowledge finds useful application in contraction of dams where dams are built with thicker walls at the bottom than the top in order to withstand the higher pressure at the bottom.
PRESSURE IN LIQUIDS IS UNIFORMLY UNIFORMLY DISTRIBUTED DISTRIBUTED THROUGHOU THROUGHOUT T When a plunger is pushed to exert pressure on the water, water will come out with the same speed (equal pressure) on all the holes. holes.
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This is a useful application in a car braking system. When a brake pedal is placed, it exerts pressure on the brake fluid, the fluid then then transmits transmits the pressure pressure equally equally to the breaks to the all tyres. This property is summarize by Pascal’s principle which states that, “The external pressure acting on a closed surf surfa ace of liqu liquid id is transm ransmitt itte ed equally throughout the liquid”
PRESSURE OF LIQUIDS DOES NOT DEPEND ON THE SHAPE OF THE CONTAINER If water is poured into a container which has parts of different shapes and sizes, it will find its own level in all the parts. This means that the pressure is the same or equal in each part.
If pressure was varying in different parts, each part of the container would have its own height. Thus pressure in liquids is independent of the shape or volume of the container. APPLICATION OF PRESSURE IN LIQUIDS 1.SPIRIT BUBBLE LEVEL This is an instrument used to check the horizontal levelness of a given surface. That is it is not inclined, it can also be used to test if a wall is vertical or slanted. It is used by masons and civil engineers in construction of buildings. It has a smaller air bubble trapped by spirit or alcohol in a small glass tube. When the surface is horizontal the bubble stays stays at the centre of of the tube.
2. BOILER GAUGE A small glass tube is connected to the side of a boiler to indicate the level of a liquid in a boiler. Since the boiler is opaque, it is not easy to see the exact level of the liquid in the boiler. The level of the liquid in a glass handle shows the level of the liquid in a boiler. This exploits the principle of a liquid maintaining same height in different parts of a containing vessel due to the
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same pressure. 3. WATER SUPPLIES Water is supplied to houses from a tank which is placed on a tower or a hill. Water is pumped into a tank and a supply pipe takes it from the reservoir tank to the houses.. The position of the tank must must be at higher level than all the houses its supplying. 4. HYDROELECTRIC POWER STATIONS Water falls from a dam have high pressure. Therefore, water reaches out to the turbines with high speed. The fast moving water drives the water turbines which produce electricity. As the level of water in the dam decreases, the pressure of the falling water also decreases. Consequently the speed of water coming out of the dam decreases as well. If the water level becomes very low, the dam stops producing electricity electricity.. This is because, the pressure pressure gets considerably considerably low hence, reduce the the speed or force of water which now is unable to rotate the turbines. PRINCIPLE OF HYDRAULIC PRESS In general, small force acting on small area can be used to overcome big force on a large area. This is the principle applied in many hydraulic hydraulic systems. systems. One such as the the hydraulic hydraulic lift used used in lifting lifting cars in garage. ATMOSPHERIC PRESSURE An inflated football or car tyres are good examples that show that gases do exert pressure. The air molecules are in continuous random motion colliding with each other and with the walls of the tube. These collisions produce pressure on the tube’s walls. Though the air molecules in a room do collide and exert pressure on bodies, this is not regarded as atmospheric pressure, the the atmospheric atmospheric pressure pressure is due to weight of air or contents contents of the the atmosphere. atmosphere. The air behaves behaves as a liquid whose pressure depends on depth. Mountains top have shorter height of atmosphere above it, thus it experiences higher atmospheric pressure. Hence pressure at sea level is very high. Climbers on high mountains such as Mount Kilimanjaro experience low pressure when nearing the top. The low pressure causes the low air density, therefore the climbers experience poor breathing. EVIDENCE OF ATMOSPHERIC ATMOSPHERIC PRESSURE. CRUSHING CAN EXPERIMENT.
Pour water into a thin metal can a quarter full. Heat the water up to boiling. A lid or cap is then tightly fitted onto the can. Then pour cold water on the can. This causes the can to collapse or become crushed When cold water was poured on the can ,it caused the steam to condense .This created low pressure inside the can .Therefore, the can crushed
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POURING MILK FROM A CAN . If a small hole is pierced on a milk milk can, it is difficult if not possible possible to pour out the milk .But when when two holes opposite each are made on top of the can, the milk comes out very easily. A GLASS OF WATER AND CARD EXPERIMENT. Fill a glass with water to the brim. Slide a paper card over top of the glass to prevent any air bubbles in the water. Slowly turn the glass upside down with your hand firmly placed on the card . Gently remove your hand and continue holding the glass upside down. It would be observed that the card does not fall off .Since no air was trapped inside the glass, the pressure on the card is due to weight of water only. On the outside, the atmospheric pressure is greater than pressure of the water. Therefore, the card experiences a net upward force which holds the card in place. Hence, water is prevented from coming out of the glass.
APPLICATION OF ATMOSPHERIC PRESSURE.
Atmospheric pressure finds important applications in the following areas. RUBBER SUCKER [PRESSURE PARDS] . This is a shallow circular rubber cap. When using it, it is moistened to get a good seal and then pressed firmly against a smooth flat surface so that the air trapped inside it is pushed out .Since the atmospheric pressure is greater, it holds it firmly against the surface.
Rubber suckers are used in industries in lifting metal sheets or glass sheets. Most of printing machines also lift pieces of of paper by use use of rubber rubber suckers. They are also used in kitchens for clearing clearing blocked sinks and other water draining systems.
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DRINKING STRAW.
When you drink fruit juice or any other drink using a straw, you suck into the straw hence removing air from it. This creates low pressure in the straw. The atmospheric pressure pushing down on the liquid in the container now becomes greater than the pressure in the straw. This forces the liquid up through the straw into your mouth.
THE SYRINGE. The syringe commonly used by nurses for giving injection, works on the same principle as the drinking straw. The pressure inside the syringe is reduced by pulling the piston outward .this causes the medicine to rush into the syringe.
BICYCLE PUMP. When in operation the bicycle pump uses two valves. One valve is in the bicycle tyre and the other one is the greasy leather washer which also act as piston in the pump. When the handle is pushed inwards, the washer presses tightly tightly against against the walls walls of the barrel so that that the air inside cannot escape. escape. The air in the barrel barrel gets compressed. This causes pressure inside the barrel to become higher than pressure in the bicycle tyre. The valve in the bicycle tyre thus opens to let in air into the tyre. When the handle is pulled out the pressure in the barrel decreases below that of the tyre and atmospheric pressure such that the tyre valve is forced to close. The atmospheric pressure pushes air into the barrel. The washer allows the air to get in. The barrel is now full ready for another down stroke.
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LIFT PUMP. Lift pumps are used for raising water from wells. The lift pump is made up of cylindrical metal barrel with a side outlet of water from the barrel after being lifted up from the well. There are two valves one is the piston and the other at the bottom of the barrel closing the entry to the plunger which goes into the well. To understand how the pump works, let us look at it with the piston down and valves B. Before starting to pump, water is poured at the top of the piston to prevent air from leaking leaking past it by pressing on valves valves A. The piston piston is pulled pulled by means of a system system o f levers levers as shown shown in the diagram diagram.. Atmospheric pressure acting acting on the the surface of the water presses up water through valve B and into the barrel. The water above the piston is lifted upward and flows out through the side sprout.
On the down stroke, valve B closes due to pressure of water on it. At the same time valve .A opens allowing water to pass into the upper part of barrel above the piston . This process is repeated frequently to let out the water. The lift pump can only raise water to height of about 10m at normal atmospheric pressure. In practice, however, the height cannot be attained due to leaks of water at the valves and piston. Also in some places where atmospheric pressure is low due to lower altitude above sea lever, the height would be less than than 10m.
FORCE PUMP. This type of pump is capable of raising water to heights well over 10 m above the water well. This makes the pump more suited to lift lift water from deeper deeper wells than than the lift lift pump.Figure pump.Figure 7.29 shows shows how this this pump works. works. The piston is pushed down forcing both valve A and B to close . As the piston is pulled up,the pressure in the barrel above above valve B becomes becomes reduced to below that of the atmospheric atmospheric pressure. pressure. The atmospheric atmospheric pressure pressure acting on the water surface in the well forces the water past valve B into the chamber. See figure 7.29 valve A remains closed because the pressure above it is still that of the atmosphere. When the piston is now pushed down again,valve B is forced to close and the pressure inside causes valve A to open and water enters into chamber. As water enters the chamber it causes air in the chamber to be compressed. The compressed air forces water out of the chamber through the outlet pipe making the flow to be continuous. On the next upstroke,the same process is repeated.The height to which water is pumped by this pump depends on on the force that can be
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exerted on the piston and not on the atmospheric pressure.
THE SIPHON This is an arrangement arrangement used to empty fixed tanks which are difficult to remove their content in normal way. The tank containing the liquid is fitted with a flexible tube i.e. bent tube which draws out the liquid from the tank. One end of the tube is set into the liquid and the other set out below the level of the liquid or the upper reservoir. The tube is bent such that one arm is shorter. The liquid then pours out through the tube. For the siphon to start working, the tube must first be filled with the liquid. The pressure acting at end A is almost that of the atmospheric pressure. The pressure at the end E is the atmospheric pressure and pressure due to liquid column DE of length, h. At A, the pressure is atmospheric, p and at B, the pressure is atmospheric .liquid pressure. Since Since the inside pressure pressure at end E is greater greater than atmospheric atmospheric pressure, the the liquid comes comes out at end E. This principle is also used in automatic flushing tanks. When the level of water rises above the level ``A`` the tank discharges water through the pipe because the out end is lower than the other end in the tank.
MEASUREMENT OF ATMOSPHERIC PRESSURE Atmospheric Atmospheri c pressure can be measured using an instrument called barometer.There are three common types of barometers; [a]Simple barometer [b]Fortin barometer
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[c]Aneroid barometer The simple barometer and fortin barometer both use mercury while aneroid barometer does not. A. SIMPLE BAROMETER A simple barometer consists of inverted glass tube containing mercury. Above the mercury column is a vacuum causing the pressure inside to be zero. The tube’s open end is immersed in a mercury container. Since the pressure inside inside is zero, zero, the atmospheric atmospheric pressure pushes pushes the mercury mercury to a height which which is approximately approximately 76 cm. That is why sometimes atmospheric atmospheric pressure is said to be 76 cm of mercury [76 cm Hg or 760 mm Hg]. The value of atmospheric pressure in Pascals can be found from the mercury height of a simple barometer. Density of mercury is 13,600 kg/m3 and g=10m/s2,height is 0.76 m.
P= gh =13,600 x 10 x o.76 =103,360N/m2 or 103,360 Pa The atmospheric pressure is approximated as 100,000 Pa. B.FORTIN BAROMETER Fortin barometer is similar to simple barometer but with some modifications. It is a very accurate barometer. The barometer tube dips into a leather bag containing mercury. As the pressure rises and falls, the levels of mercury in the bag [reservoir] changes. The adjusting screw is adjusted to bring the level of mercury to the ivory tip .This makes mercury level to be in a correct position needed in taking measurements. Near the closed end of the tube is a vernier scale which is adjusted using thumb screw. Behind the barometer tube, there is a plane mirror used when taking reading. Using a thumb screw, the bottom of vernier scale is brought to level with the meniscus of the mercury. The barometric height is then read from the vernier scale correct to 0.1 mm.
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C. ANEROID BAROMETER Aneroid barometer consist of a thin corrugated metal box which has been partially evacuated creating a partial vacuum in it. The sides of the box are held a part by use of a spring. The box expands when atmospheric pressure decreases decreases and contracts when when atmospheric atmospheric pressure pressure decreases decreases and contracts when atmospheric atmospheric pressure pressure increases. The two sides move due to pressure changes. Since the movements are small, they are magnified by a system of levers. They levers cause a pointer on the circular scale to move. The scale is marked in centimeters of mercury or other standard barometers. barometers.
MEASURING GAS PRESSURE USING MANOMETER A manometer is a special instrument which uses liquid pressure to measure gas pressure. It consists of U-tube which is open on one end and the other end connected connected to a gas supply. The U-tube is partially filled with a liquid in the U – U – tube tube causing the level in the two limbs of the tube to be different. The difference in height of the liquids shows how much pressure of the gas is greater than that of the atmospheric pressure. The pressure of the gas p is greater than atmosphere pressure p by an amount hg i.e. Pgas = Patm + ℎ Not that, Paton Paton is the the atmospheric atmospheric pressure pressure .If the atmospheric atmospheric pressure pressure is known, known, the pressure pressure of gas can can be found.
1. A block of mass 20Kg has sides of 0.5 m, 0.3m and 0.05m. (Take g=10m/s). Find; (a) Weight of the block (b) Maximum pressure it can exert (c) Minimum pressure it can exert 2.(a)Explain why tractors have wide tyres? (b)Explain why sharp knife cuts meat easily than blunt one? 3.The density of honey in a tin of cross-section area 2.48m 2 is 1004Kg/m3. If the tin column is 0.5m high. Education is an ope n sesame to success”
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Calculate the pressure and force the tin exerts at the bottom. 3. Calculate the pressure at the bottom of the tank of water 15 m deep due to the water above it.
8. WORK, ENERGY AND POWER Work is is the product of force and distance moved in the direction of force.
= == Where; F =for =for ce D=distance The SI unit of work is N ewto unit of wton me metre (N M )
But; 1NM =1J The SI unit of work is J oule ule Examples: 1.A sack of maize which weights 800N is lifted to a height of 2m.what is the work done?
Solut Solution ion Data given; Force=800N Distance=2M Work=? From;
= == = 800 800 22
= 1600Nm But 1NM=1J Therefore work done is 1600J
2. How much work is done to first lift a 7kg object is a distance of 2m and then hold it at that height for 10 seconds.
Solut Solution ion Data given; Mass=7kg Distance=2m Time=10s But; From; Education is an ope n sesame to success”
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= ==
Since; F = mg = 7 x 10 =70N W=FD
= 70 2
Work done=140J
ENERGY. Energy is is the ability or capacity to do work The SI unit of energy energy is joule unit of joule (J ) The concept of energy is used in all fields of science among them are; Physics: Change in motion, heat and the states of matter, electric and magnetic phenomena, atomic and nuclear transformation. Chemistry : Interaction in matter at the atomic or molecular level, the change of one va Geology : Earthquakes, volcano, formation of mountains, erosion and continental drift. Mete Meteorolo rology : Wind, precipitation, lighting, hurricane and tornadoes. Astrono Astronom my : Stars and galaxy formation the motion of nomical objects Biology : Growth and development, metabolism in living, photosynthesis and reproduction Therefore work is done with the availability of energy hence the possession of energy can be viewed as a promise of work work to be done. done. FORMS OF ENERGY Energy exist in many different forms. All energy may be classified as either kinetic energy or or po potential ntial energy . Within the two classification of energy there are many different forms of energy which are;
i. ii . iii. iv. v. vi. vii. viii.
Thermal energy E lect lectrr i cal cal ener ner gy Chemical energy Nuclear energy E lectrom lectroma ag netic netic ener ner g y Soun Sound d energ nergyy E lastic pote potenti ntial al energy nerg y Mecha Mechanica nicall energ nergyy 1. KINETIC ENERGY (K.E) K i netic netic ene enerr gy :is :is the energy possessed by the body by a reason of it motion The kinetic energy of an object depend on its mass and velocity. Kinetic energy is expressed as;
= .= joule (J ) The SI unit of K.E is joule
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Examples; 1. An object as a mass of 5kg what is its kinetic energy if its speed is 10m/s 2
Solut Solution ion;; Data given Mass =5kg Velocity=10m/s 2 K.E=? From
1 = 12 .= 21 .= 2 5 10 = 250 The kinetic energy is 250J. 250J.
2. What is the kinetic energy of 0.12g bullet travelling at 320m/s?
Solut Solution ion;; Data given Mass =0.12g = 0.00012kg Velocity = 320m/s K.E=? From;
1 = 12 .= 21 .= 2 0.00012 320 = 6.144 The kinetic energy is 6.144J
2.POTENTIAL ENERG (P.E) possessed by the body by by a reason of its po Potential energy is the possessed position sition or sta state. The potential energy is expressed as;
= = .. == jouless (J ) The SI unit of P.E is joule E xamp xamples; les;
1. A stone of mass 2kg fall from a height of 25m above the ground calculate the potential energy possessed by the stone.
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Data given Mass = 2kg Height =25m Acceleration due to gravity=10N/kg P.E=? From
= ℎ .. == ℎ ℎℎ . = 2 101025 P.E = 500J
TRANSFORMATION OF ENERGY
THE PRI NCIPLE OF CONSERVATION CONSERVATION OF E NERGY ner gy can nei nei ther ther of be cr cr eate ated nor nor destr destroy oyed ed but it can The principle of conservation of energy state that “ E ner be transfor transform med fro fr om one form to another” A device which coverts or transforms one form of energy to another is called a transducer. Examples of energy transformations includes; Potentii al E ner ner gy into ki netic tic ener ener gy . The bow converts converts Potent into kine
into electric energy . . Microp M icropho hone ne converts soun sound d energ nergy y into into sound R ecei cei ver ver converts electric energy into sound energ nergy y . . Dynamo converts mechanical energy into into electric energy. Turbines converts mechanical energy into into electric energy and heat energy F i lame laments of the electric lamp converts electric energy into light and into electric energy . . B atte atterr i es (dry ( dry cells) cells) coverts chem chemi cal cal ener ener g y into Generator converts lectricc ener ener g y . . converts chemical energy into electri Chlorophyll converts sun light energy into chem chemi cal cal energy. nerg y.
THE SIMPLE PENDELUM BOB
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Consider the motion of simple pendulum. A pendulum is a mass suspended by a string or wire from a fixed point so that that it can move back back and forth along arc. arc. is called the equilibrium level. T he lowe lowest poi poi nt is NB: The total mechanical energy of the pendulum remains constant.
At point A and and D The pendulum’s highest point above equilibrium level, all energy is P.E Thus,
= . + .. == .. +
But K.E = 0
At point C The point C is the lowest point, therefore all the energy is K.E Thus,
= . + .. == . + .. But at point C P.E = 0
At point B At points like B, Between highest and lowest points, the energy is a mixture of K.E and P.E Thus;
= . + ..
Examples: 1.At its highest point, a pendulum of mass 0.8 Kg is 1.2m above the equilibrium level. (a) What will be its velocity, as it swings its lowest point? (b) What is its velocity when it is 0.9m above reference level/equilibrium level (c) At what height above the equilibrium level will its velocity be 2m/s Solution: Data given; Mass= 0.8kg Height= 1.2m (a) What will be its velocity, as it swings its lowest point?
The pendulum’s highest point above equilibrium level, all energy is P.E Thus,
= P. E + K.K. E == PP.E. E + 0
But K.E = 0
But;
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.=ℎ ... == 0.9.8419.81. 81.2 == 0K. +E K.EK.E = 2.2. = 2 0.9.841
But; At the lowest energy P.E=O
Therefore; 2K.E=
V= 4.85 Velocity at the lowest point is 4.85m/s (b) What is its velocity when it is 0.9m above reference level/equilibrium level. Solution:
P. E=+P.K.E E+ K.K=. E P.=ℎ . E + K.E =9.41 ... =7.= 0.086 99..8 00..9 K.EK.EK.K. EE =2.= 35 . = 2.2. = 2 0.2.835 = 4.0.4.78 =√5.875 =2. 4 1
Velocity at the lowest point is 2.41m 2.41m//s (c) At what height above the equilibrium level will its velocity be 2m/s Education is an ope n sesame to success”
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.= 121 .= 2 0.8 2 . ==P.1E.6+ K.K. E P.P.EE =9.=411.K.E6 P.E =7.81 .=ℎ ℎ = .. = ...
Solution:
But;
h=1m The height will be 1m POWER Power is the rate of doing work. Power is the measure of the rate at which energy changes. This means that whenever work is done, energy changes in a different form. Therefore;
= =
The S.I unit of power is Jo J oule per seco second nd (J /S) or Watt Watt ( W)
1J/ 1J /S = 1Watt 1Watt Other units of power are;
1Ki 1K i lowat lowattt = 1000 Watts Watts 1Megawatt = Watts 1Ho 1H or se power ( H P) = 750Watt
Examples: 1. A forklift was used to raise the load of 400kg to a height of 2m in 4 seconds. Determine the power determined. Solution: Data given; Mass= 400kg Height= 2m Time= 4s But;
.. == 4ℎ 0010ℎ102 P.E = 8000J
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Work done is 8000J
= = =
= 2000 Watts
2000 Wat Watts Therefore the power developed is 2000
1. A force of 80N pulls a box along a smooth and level ground through a distance of 5m. calculate the work done by the force. 2. Chambundu lifts a brick of mass 10kg from a flow to a shelf 3m high. How much work does he do? 3. If a man pushes a van against a force of 300N for a distance of 10m, how much work does he do? 4.What is the kinetic energy of 2kg missile travelling at 600m/s? 5. Chipato has a mass of 80 kg. If he runs at a speed of 15m/s , calculate his kinetic energy. 6. A stone of mass 10kg is dropped from rest to the ground 10m down. If it hits the ground with a velocity of 20m/s. Determine its; (a) Kinetic energy (b) Potential energy 7.How much power is required to accelerate a 1000kg car from rest to 26.7m/s in 8seconds? 8. A truck for transporting sand is filled to capacity. If the digger has to move through through a height of 2m and the total load was 5000kg calculate; (a) The work done in loading the sand (b) The power in developed in 5seconds 5seconds 9. Rock A has a mass of 2kg and a speed of 1m/s. Another rock B has a mass of 1kg and a speed of 2m/s, which rock has more kinetic energy? 10. A car with mass of 10 kg moves with kinetic energy of 2000J. Calculate the speed of the car.
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9. LIGHT PART I Light is the form of energy which stimulated the sensation of vision. Therefore light is an invisible form of energy that causes the sensation of vision in us through our eyes. NATURE OF LIGHT Light is a form f orm of energy that can be distinguished from other forms of energy through its features or characteristics namely; (i) Light radiates (spreads out) from its source (ii) Light travels in straight line (iii) Light travels energy (iv) Light travels in vacuum. (v) Light travels at fastest speed. At speed speed limit of 3 x 10 8 m/s SOURCE OF LIGHT Light can come from a source in two ways; (a) A source may give out its own light. (b) It may may reflect light from another object. For example we see the sun because it emits light, where as we see the moon because it reflects light from the sun. Therefore sources of light can be classified as natural or artificial. natural al sources of light are; Examples of natur (i) The sun (ii) The stars (iii) Lightings tif i cial sour source cess of light are; Examples of ar tifi (i) Wood fire (iii) Candles (iii) Hurricane lamps (iv) Gas lamps (v) Electric lamps LUMINOUS AND NON LUMINOUS BODIES Luminous objects are those that emits (send out) their own light. Examples of luminous bodies are; (i) The sun (ii) Stars (iii) Glowing TV (iv) Glowing worms (v) Fire flies (Bioluminiscence flies) Non luminous luminous objects are those that do not not emit their their own light. They only become become visible when when they reflect light from another source into our eyes. Examples of non luminous bodies are; (i) The moon Education is an ope n sesame to success”
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(ii) The planets Objects that emit light as a result of being heated are called I ncande ncandescent scent . Examples of incandescent bodies are lig li g ht bulbs, bulbs, fi f i r e and and cand candle les. s. PROPAGATION AND TRANSMISSION OF LIGHT RAYS AND BEAMS OF LIGHT. Light travels in straight lines. This is one among the properties of light. The spreading of light from its source to the environment in straight lines is referred to as rectilinear propagation of light. of light. A ray ray is the path taken by light in moving from the source to another point. A ray is usually represented as a line with an arrow head. A beam is a collection or bundle of rays of light. A beam of light can either be pa or paralle rallell, convergent or
divergent.
TRANSPARENT, TRANSLUSCENT AND OPAQUE The ability of light to travel through material varies from one substance to another. When light travels through matter, it is said to be transmitted (passed through). When discussing light transmission materials are classified into three categories namely as; (i) Transparent materials. (ii) Transluscent Transluscent materials. (iii) Opaque materials. 1. TRANSPARENT MATERIALS Materials that allow light to pass through them are called transp tr anspa ar ent mate materr i als. Examples of transparent materials are glass are glass and and clear plastics. clear plastics. 2. TRANSLUSCENT MATERIALS Tr ansluscent ansluscent mat mate er i als are materials that allow only part of light to pass through them. Examples of transluscent materials are oily paper , tinted glass (frosted glass) 3. OPAQUE MATERIALS Opaque Opaque mate mater i als are those that do not allow light to pass through at all. Examples of opaque materials are walls human body. REFLECTION OF LIGHT. We stated earlier that we see objects only when portion of light from them enters our eyes. When light falls on a body it either passes through or bounces back. When light bounces back it is said to be reflected and bouncing back process is called reflection of light . TYPES OF REFLECTION All polished or shiny surfaces reflect light, but the way they reflect light is not the same. For example, the reflection in a plane mirror is not the same as reflection on a polished brick or white paper. Reflection can be classified as;
(i) Regular reflection (i i ) I rr egular gular or di ffuse ff use r eflect flection ion Education is an ope n sesame to success”
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1. REGULAR REFLECTION Regular reflection occurs when light rays fall on a smooth surface, the light rays are reflected parallel to each other.
2. IRREGULAR/DIFFUSE IRREGULAR/DIFFUSE REFLECTION Irregular reflection occurs when reflected rays from the surface are not parallel to each other. This means that reflected rays are sent in different directions.
LAWS OF REFLECTION When light is reflected two important laws must be obeyed, before stating the laws it is important to know the terms used in the laws. These are; 1. I ncident ncident ray: ray: This is the ray that falls on the surface at the point of incidence. incidence. 2. Norma Normal: It is perpendicular perpendicular line drawn to the reflecting surface at the point of incidence. 3. R eflec flected ray: ray: This is the ray that bounces back from the reflecting surface. 4. Po P oi nt of of i ncidence ncidence:: This is the point on surface at which incidence ray strikes the reflecting surface. 5. Angle of incide incidenc nce e: This is the angle between incident ray and the normal. 7.Angl 7.A ngle e of re r efle fl ection: This is the angle between the normal and reflected ray.
F i r st law law of of r eflection flection states that, “The incident ray, the ray, the normal and the reflected ray at the same point Education is an ope n sesame to success”
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of incidence all lie in the same plane .” Seco Second nd law law of reflect reflection ion states that, “The angle of incidence equals to angle of reflection .” IMAGES FORMED BY PLANE MIRRORS Plane mirror is a thin flat piece of glass whose one side is silvered and the other side is shiny. The shiny surface reflects light incident on the glass. Rays from object incident to the mirror are reflected away. The rays appears to meet at a point beyond the mirror surface where the image is formed such image formed is said to be virtual image. That is , it is formed by apparent intersection of rays. PROPERTIES OF IMAGES IN PLANE MIRRORS Images formed in plane mirrors show some unique properties, these are; 1. Plane mirrors form virtual images. 2. The image is upright. 3. The image is inverted laterally. 4. The image is the same size as the object’s size. 5. The image distance equals to the object’s distance from the mirror. MULTIPLE IMAGES If two mirrors are placed at an angle to each other and an object is placed between them several images of the object are formed. The number of images formed obeys a rule that; if the number 360 0 is divided by the angle angle between between the mirrors, mirrors, n number number of images images are formed. formed. The number of images n formed by two plane mirrors at an angle Ɵ is given by;
ₒ = Ɵ ₒ
– 1 1
If the mirrors are placed at to each other, and an object is placed between them the numbers of images formed in the mirror is 3. When the mirrors are parallel to each other, the angle is zero and the number of images of an object placed between them is undefined (infinite number of objects) APPLICATION OF PLANE MIRRORS. Mirrors are used at home for grooming and decorations purposes. In physics laboratory and marines mirrors are used to make a periscope. to the stem of The peri periscop scope e is made up of two mirrors fixed facing each other at inclined angle of the periscope. Light is reflected by the two mirrors. More complex periscopes are used in submarines.
ₒ
K alei alei doscop doscope e is another instrument which uses plane mirrors. Three mirrors inclined at an angle of
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to each other are fixed in an opaque tube. The ground glass plate at the bottom of the tube allows light into the tube. Small pieces of colored glass are plane on the glass plate. These pieces act as an
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object. These are reflected to form five images, Observing through the tube five images together with the object are seen forming symmetrical pattern with six identical sectors. When the tube is shaken the pieces rearrange themselves themselves and new pattern is obtained. obtained.
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Succeed in Physics
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Safari L. Mwelu [0785 523 231/0718 707 520]
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