Chapter 1 Introduction to Physics Teacher's Guide 2009

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _____________________________________ ___________________ _______________________________________ __________________________________________ _______________________________ __________

CHAPTER 1 : INTRODUCTION TO PHYSICS 1.1 Understanding Physics PHYSICS Mechanical Energy

Study of the natural phenomena phenomena and the the properties of matter.

Matter

Solid

Heat Energy

Light Energy

Energy

Wave Energy

Liquid

states

forms Electrical Energy

Gas Nuclear Energy

Chemical Energy

Properties of Matter

Relationship with matter

Relationship with energy

Properties of Energy

in the fields

Mechanics

Properties of matter

Wave

Heat

Electronics

Electricity & Electromagnetism

Light

1

Atomic Physics & Nuclear

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________

1.2

PHYSICAL QUANTITIES

Base quantity

1 2 3

any quantity that can be measured by a scientific instrument. A physical quantity is …………………………………………………………………….. Stopwatch, metre rule balance, thermometer, ammeter Examples of scientific instruments:……………………………………………………… etc. A base quantity is a physical quantity which cannot be defined in terms of other physical

quantities. 4

Study the following picture and list the physical quantities that can be measured. The list of physical quantities : Height, 1. ………………………………………. mass, 2. ………………………………………. size, 3. ………………………………………. age, 4. ………………………………………. temperature, 5. ………………………………………. current 6. ………………………………………. Power, 7. ………………………………………. Thermal energy 8. ………………………………………. Pressure 9. ……………………………………….

battery

5

List of 5 basic physical quantities and their units. Base quantity

Symbol

S.I. Unit

Symbol for S.I. Unit

Length

l

Mass

m

kilogram

kg

Time

t

second

s

Current

I

Ampere

A

Temperature

T

Kelvin

K

meter

m

6. Two quantities that have also identified as basic quantity. There are: Light intensity candela ii) ………………………. Amount of substance unit …………….. mol i) …………………………..unit …………..

2


Standard Form

1

n

2

Standard form = A x 10 , 1 < A < 10 and n = integer simplify the expression of very large and small numbers Standard form is used to …………………………………………………………………...

3

Some physical quantities have extremely small magnitudes. Write the following quantities in standard form : 6

6.37 x 10 m a. Radius of the earth = 6 370 000 m =…………………………………………………. -31 9.11 x 10 kg b. Mass of an electron = 0.000 000 000 000 000 000 000 000 000 000 911 kg =………... -5

3.0 x 10 m c. Size of a particle = 0.000 03 m = ……………………………………………………… -8 7.2 x 10 m b. Diameter of an atom = 0.000 000 072 m = …………………………………………... -7

c.

5.5 x 10 m Wavelength of light = 0.000 000 55 m = ……………………………………………..

Prefixes represent a large physical quantity or extremely small quantity in 1. Prefixes are usually used toS.I………………………………………………………………... units. the unit as a multiplying factor. 2. It will be writtenbefore ……………………………………………………………………………

3. The list of prefixes : Tera (T)

10

12

1 × 10 m 1 Tm = ……………………………………. 9

Giga (G)

10

-3

6

Mega (M)

3

kilo (k)

10

10 102 1

0

10

-3

10

10

-1

10 -2 10

mili (m) micro (µ)

-9

nano (n)

10

-12

Hekto (ha) Deka (da)

3.6 × 10 A 3.6 mA = ……………………………………. How to change the unit ; Eg : 1. Mega to nano 6 1.33 MA = 1.33 × 10 A

desi (d) centi (c)

= 1.33 × 10 = 1.33 × 10

-6

10

10

Eg :

-15

6-(-9)

nA

nA

2. Tera to micro 1.23 Tm to unit µm unit 1.23 Tm = 1.23 x 10

pico (p)

= 1.23 x 10 = 1.23 x 10

12

m

12 – (-6)

m

18

m

3. piko to Mega 5456 pA to MA unit 5456 pA = 5.456 x 10

3 + (-12)

pA

-9

= 5.456 x 10 pA

3

= 5.456 x 10

-9 –(6)

= 5.456 x 10

-15

MA

MA


4. Some physical quantities have extremely large magnitudes. These extremely large and small values can be written in standard form or using standard prefixes. Write the quantities in standard prefixes: 9.1 × 10 MHz a. Frequency of radio wave = 91 000 000 Hz = …………………………………………. 1 12.8 Mm = 1.28 × 10 Mm b. Diameter of the earth = 12 800 000 m = ……………………………………………… 2 383 Mm = 3.83 × 10 Mm c. Distance between the moon and the earth = 383 000 000 m = ……………………… 15 6.0 × 10 Tg d. Mass of the earth = 6 000 000 000 000 000 000 000 000 kg = ………………………

Derived quantities

1

a physical quantity which combines several basic quantities A derived quantity is …….………………………………………………………………… through multiplication, division or both ………………………………………………………………………………………………

2

Determine the derived unit for the following derived quantities. Derived quantity

Formula

Derived unit

Name of derived unit

area

area = length x width

m x m = m2

–

volume

volume = length x width x height

mxmxm=m

density

velocity

density =

velocity =

mass

3

kg

volume

m

3

displacement

m

time

s

=

kg m

=

m s

m s −1 Acceleration

acceleration =

change in velocity time

s

−3

−1

=

m s -1 s −1

=

m s −2

– –

–

–

momentum

momentum = mass x velocity

kg m s-1

–

Force

force = mass x acceleration

kg m s-2

Newton (N)

pressure

pressure =

force

kgms

area

m

weight

weight = mass x gravitational acceleration

work

work = force x displacement

power

power =

work

4

2

kg ms N m

Js

time

−2

-1

-2

-1

-2

kg m s (Nm-2) @ Pa Newton (N)

Joule (J)

Watt (W)


Derived quantity kinetic energy

Formula

K.E =

1 2

Derived unit

× mass × velocity

2

Name of derived unit

2 -2

Joule (J)

2 -2

kg m s

potential energy

P.E = mass x gravitational acceleration x height

kg m s

Joule (J)

charge

charge = current x time

Ampere second (As)

Coulomb (C)

voltage

resistance

voltage =

work

JC

charge

resistance =

voltage

-1

Volt (V) -1

VA

current

Ohm (Ω)

Note that the physical quantities such as width, thickness, height, distance, displacement, perimeter, radius and diameter are equivalent to length. 1.3

1

2

3

SCALAR AND VECTOR QUANTITIES Physical Quantity which has only magnitude or size Scalar quantities are ……………………………………………………………………… Mass, Length, Speed, volume Examples : ………………………………………………………………………………… Physical Quantity which has magnitude or size and direction. Vector quantities are………………………………………………………………………... Velocity, Force, Displacement, Acceleration Examples : …………………………………………………………………………………

Study the following description of events carefully and then decide which events require magnitude, direction or both to specify them. Description of events

Magnitude 0

1. The temperature in the room is 25 C

√

2. The location of Ayer Hitam is 60 km to the north-west of Johor Bahru

√

3. The power of the electric bulb is 80 W

Direction

√

√

4. A car is travelling at 80 km h-1 from Johor Bahru to Kuala Lumpur

5

√

√


1.4

MEASUREMENTS

Using Appropriate Instruments to Measure

1

measuring instrument with different measuring capabilities. There are various types of………………………………………………………………….

2

measure a particular quantity. We must know how to choose the appropriate instrument to ……………………………..

3

Examples of instrument and its measuring ability. Measuring instrument

Range of measurement

Measuring tape

Up to a few meters

Meter rule

1m

0.1 cm 0.1 cm (0.01 m)

10 cm

Vernier caliper

0.01 cm

less than 2 cm (20 mm)

Micrometer screw gauge 4

Smallest scale division

0.001 cm (0.01 mm)

Sample of measuring instruments: is use to measure electric current 4.1 Ammeter : …………………………………………………………………………….. incorrect reading correct 1 2 3 1 2 3 0 4 reading 0

4

mirror

pointer

pointer

mirror

Pointer’s image is behind the pointer

Pointer’s image can be seen

is used to determine the volume of liquid. 4.2 Measuring cylinder : ……………………………………………………....................

wrong position of eye Right position of eye (eye are in a line perpendicular to the plane of the scale) wrong position of eye water

is used to determine the length 4.3 Ruler : ……………………………………………………………………………………… wrong

10

11

right

12

13

wrong

14

6

15

Reading = ……………… cm


4.4 Vernier calliper A venier calliper is used to measure: a.

small object ………………………………………………b.

c.

………………………………………………d.

depth of a hole ………………………………………….

external diameter of a cylinder or pipe

internal diameter of a pipe or tube

………………………………………….

0.01cm A vernier calliper gives readings to an accuracy of …………………………………...…. cm.

inside jaws Vernier scale1 cm 0

2

3

4 Main scale

outside jaws Main scale in cm

0.9 cm Length of vernier scale = ………

0

Vernier scale is divided into 10 divisions 0

0.09

Length of the divisions = ………. cm

10

5

The different between the main scale and vernier 0.01 cm scale is = ……………………………. cm

0

1

0.2 cm

Main scale

Vernier scale

0

= ………………….

1 2 3 4 5

6 7 8 9 10

Find the division of vernier scale which is coincides with any part of the main scale

0.06 cm

Vernier scale = …………………..

0.26 cm

Final reading = …………………..

Example: The diagram below shows a vernier calliper with reading. 0

1

0

5

0.15 Vernier calliper reading = ……………. cm

10

7


4.5 Micrometer screw gauge. A micrometer screw gauge is used to measure : objects that are small in size a. ……………………………………………… diameter of a wire b. …………………………………………. diameter of small spheres such as ball bearings c. ………………………………………………

One complete turn of the thimble (50 division) moves the spindle by 0.50 mm. Division of thimble 0.5 ÷ 50 = ………………….. 0.01 mm = ………………….. A accuracy of micrometer 0.01 mm screw gauge = ……………..

4.5 mm Sleeve scale : …………… 0.22 mm Thimble scale : …………. 4.62 mm Total reading : …………..

Example : 2.0 mm Sleeve scale : …………… 0.22 mm Thimble scale : …………. 2.22 mm Total reading : …………...

4.6 Some others measuring instruments :

Analogue stopwatch digital stopwatch ……………………… ……………………

Measuring tape ……………………….

thermometer Ammeter ……………………… ………..

measuring cylinder ……………………..

beaker ………………

Hands-on activity 1.1 on page 1 of the practical book to learn more about choosing appropriate instruments.

8


Exercise: Vernier Callipers

1. Write down the readings shown by the following (a) 7

8

5

0

(b)

4

A

B

P 0

10

Answer: …7.79 cm…………..

5

Answer: …4.27 cm…………..

Q 10

5

(c) 6

7

Answer: ……6.28 cm……….. 0

(d)

1

5

Answer: …0.02 cm…………..

1

0

0

10

5

2. (a) The following diagram shows the scale of a vernier calliper when the jaws are closed. 1

0

0

10

5

Zero error = …+ 0.02……… cm (b).

The following diagram shows the scale of the same vernier calliper when there are 40 pieces of cardboard between the jaws. 5

6

0

5 9

10


= …5.64…….cm

Reading shown

Corrected reading = …5.64 - (+ 0.02)= 5.62……..cm 3.

Diagram 3 (a) shows the reading on a pair of vernier callipers when its jaws are closed with nothing in between them. Diagram 3(b) shows the reading when it is used to measure the thickness of a piece of wood. 0 cm

0

1

5

4

2

5

0

10

(a)

5

6

10

(b)

What is the actual thickness of the wood? Zero error

-0.05 = ………………….. cm

Reading shown

4.51 = …………………..cm

4.51- (-0.05) =4.56 Actual thickness of the wood = ……………………………….cm Exercise: Micrometer Screw Gauge

1. (a) Determine the readings of the following micrometer screw gauges.

0

0

0 45

5

0

Zero error = …-0.02…….. mm

Zero error = …+0.03…….. mm

(b) Determine the readings of the following micrometer screw gauges.

0

5 0

Zero error = +0.03………mm

5

20

15

Reading shown

= 6.67 ………..mm

Corrected reading = 6.67-(+0.03)=6.64 mm

10


2. Write down the readings shown by the following micrometer screw gauges. (a) (b) 0

40

5

0

5

35

10

35

30

Answer: …6.88 mm…………

Answer: …..12.32 mm……

(c)

(d) 0

25

0

5

20

20

15

Answer:………4.71 mm…………

Answer:

9.17 mm…………

Accuracy and consistency in measurements. The ability of an instrument to measure nearest to the actual value 1. Accuracy : ………………………………………………………………………………… The ability of an instrument to measure consistently with little or no relative 2. Consistency : ……………………………………………………………………………… deviation among readings. The ability of an instrument to detect a small change in the quantity measured. 3. Sensitivity : …………………………………………………………………………………

inaccurate but consistent …………………………

consistent and accurate ……………………………..

Accurate but not consistent ……………………..

inaccurate and not consistent ………………………………

Hands-on activity 1.2 on page 2 of the practical book to determine the sensitivity of some measuring instruments. 11

JPN Pahang Physics Module Form 4 Teacher’s Guide Chapter 1 : Introduction To Physics _________________________________________________________________________________________ Errors in measurements

of approximation only. 1. All measurements are values ……………………………………………………………… how close the measurement is to the actual value. 2. In other word, it is a matter of …………………………………………………………… error exist in all measurements. 3. This is because ……………………………………………………………………………

4. Two main types of errors: Systematic errors 4.1 …………………………………………… Occurs due to : a weakness of the instrument a) ……………………………………………………………………………………… the difference between reaction time of the brain and the action. b) ……………………………………………………………………………………… zero error is when the pointer is not at zero when not in use. c) ………………………………………………………………………………………

Examples : to the smallest reading that can be measured by an instrument. a) Refer ……………………………………………………………………………………… Range of the measuring instrument – absolute error . b) ……………………………………………………………………………………… Reaction time of the brain. c) ……………………………………………………………………………………… Absolute error : If, the smallest reading = 0.1 cm ……………………………………………………………………………………….………… Then, Absolute error = 0.1 / 2 = 0.05 cm …………………………………………………………………………………………………. It occurs because the position of the eye is not perpendicular to the scale of Parallax error : ……………………………………………………………………………… the instrument.

Example :

wrong position of the eye (no error) wrong

where the pointer is not at zero when not in use Zero error : …………………………………………………………………………………...

Correct reading = observed reading – zero e rror

ZeroPosit error of Vernier calliper

Positive zero error 0

Negative zero error 1

0

cm

0 1 2 3 4 5 6 7 8 9 10

1

0 1 2 3 4 5 6 7 8 9 10

Zero error =+0.03 cm

Zero error = - 0.04 cm

12

cm


Zero error of screw meter gauge

Negative zero error

Positive zero error

Horizontal reference

Horizontal reference

2 divisions below horizontal reference

Zero error = + 0.02 mm

3 divisions above horizontal reference

Zero error = - 0.03 mm

Random error 4.2 ……………………………………………..

Occurs due to carelessness in making the measurement. a) ……………………………………………………………………………………… parallex error , incorrect positioning of the eye when taking the readings. b) ……………………………………………………………………………………… sudden change of ambient factors such as temperature or air circulation. c) ………………………………………………………………………………………

Example : Readings are close to the actual value but they are not consistent. a) …………………………………………………………………………………..… Can be minimized by consistently repeating the measurement at different places in b) …………………………………………………………………………………….. an identical manner. ..................................................................................................................... 1.5

SCIENCETIFIC INVESTIGATION

Steps

Explanation

1

Making observation

Gather all available information about the object or phenomenon to be studied. Using the five senses, sight, hearing, touch, taste and smell.

2

Drawing inferences

A conclusion from an observation or phenomena using information that already exist.

3

Variables are factors or physical quantities which change in the course of a scientific investigation. There are three variables : i. Manipulated variables – physical quantity which change according to the aim of the experiment. Identifying ii. Responding variables – physicals quantity which is the result and controlling of the changed by manipulated variable. variables iii. Fixed variables – physicals quantities which are kept constantduring the experiment.

13


4

5

Formulating a hypothesis

Conducting experiments

Statement of relationship between the manipulated variable and the responding variable those we would expect. Hypothesis can either be true or false but in correct direction. i.

Conduct an experiment includes the compilation and interpretation of data. ii. Making a conclusion regarding the validity of the hypothesis.

Plan and report an experiment

Situation : A few children are playing on a different length of swing in a playground. It is found that the time of oscillation for each swing is different. Steps

Example : refer to the situation above

1

Inference

The period of the oscillation depends on the length of the pendulum.

2

Hypothesis

When the length of the pendulum increases, the period of the oscillation increases.

3

Aim

Investigate the relationship between length and period of a simple pendulum.

4

Variables

Manipulated variable : the length of the pendulum. Responding variable : Period Fixed variable : the mass of the pendulum and the displacement.

5

List of apparatus and materials

6

Arrangement of the apparatus

Retort stand

protractor

l l

bob

14


7

Procedures

1. 2. 3. 4.

5.

8

Tabulate the data

Set up the apparatus as shown in the figure above. Measure the length of the pendulum,l = 60.0 cm by using a meter rule. Give the pendulum bob a small displacement 300.Time of 10 oscillations is measured by using a stop watch. Repeat the timing for another 10 oscillations. Calculate the average time. Period = t 10 oscillations 10 Repeat steps 2, 3 and 4 using l = 50.0 cm, 40.0 cm, 30.0 cm and 20.0 cm

Length,l / cm

Time for 10 oscillations / s 2 1 Av Aver age

60.0 50.0 40.0 30.0 20.0

9

Analyse the data

15.8 15.0 13.1 11.9 9.9

15.7 15.0 13.1 11.9 9.9

15.8 15.0 13.1 11.9 9.9

Per iod/ s (T = t10/10) 1.58 1.50 1.31 1.19 0.99

Graf of period, T vs pendulum’s length, l

T/s 1.4 1.2

1.0

0.8

0.6

0.4

0.2

0

10

11

Discussion

Conclusion

10

20

30

40

50

60 l / cm

Precautions : 1. Oscillation time is measured when the pendulum attained a steady state. 2. Time for 10 oscillations is repeated twice to increase accuracy. 3. Discussion (refer to given questions)

The period increases when the length of the pendulum increases. Hypothesis accepted.

15


Reinforcement Chapter 1 Part A :Objective Question

1. Which of the following is a base SI quantity? A Weight B Energy C Velocity D Mass

10. The diameter of a particle is 250 µm. What is its diameter in cm? -4 B 2.5 x 10 A 2.5 x 10-2 -6 -8 C 2.5 x 10 D 2.5 x 10

2. Which of the following is a derived quantity? A Length B Mass C Temperature D Voltage

11. Which of the following prefixes is arranged in ascending order? A mili, senti, mikro, desi B mikro, mili, senti, desi C mili, mikro, desi, senti D desi, mikro, mili, senti

3. Which of the following is not a basic unit? B kilogram A Newton C ampere D second

12. Velocity, density, force and energy are A basic quantities B scalar quantities C derived quantities D vector quantities

4. Which of the following quantities cannot be derived? A Electric current B Power C Momentum D Force

13. Which of the following shows the correct conversion of units? 3 -6 3 A 24 mm =2.4 x 10 m 3 -7 3 B 300 mm =3.0 x 10 m 3 -2 3 C 800 mm =8.0 x 10 m 3 -4 3 D 1 000 mm =1.0 x 10 m

5. Which of the following quantities is not derived from the basic physical quantity of length? A Electric charge B Density C Velocity D Volume

14. Which of the following measurements is the shortest ? 3 A 3.45 x 10 m 4 B 3.45 x 10 cm 7 C 3.45 x 10 mm 12 D 3.45 x 10 µm

6. Initial velocity u, final velocity v, time t and another physical quantity k is related by the equation v - u = kt. The unit for k is -1 -1 A ms B m s -2 2 -2 D m s C ms

15. The Hitz FM channel broadcasts radio waves at a frequency of 92.8 MHz in the north region. What is the frequency of the radio wave in Hz? 4 5 A 9.28 x 10 B 9.28 x 10 7 10 D 9.28 x 10 C 9.28 x 10

7. Which of the following has the smallest magnitude? A megametre B centimetre C kilometre D mikrometre 8. 4 328 000 000 mm in standard form is -9 -6 A 4.328 x 10 m B 4.328 x 10 m 6 9 C 4.328 x 10 m D 4.328 x 10 m

16. An object moves along a straight line for time, t . The length of the line, s is 1 2 given by the equation s = gt . The 2 SI unit of g is 2 2 A m s B m s-2 -1 -2 C s D s m

9. Which of the following measurements is the longest? -4 -5 A 1.2 x 10 cm B 120 x 10 dm -11 C 0.12 mm D 1.2 x 10 km

16


Part B : Structure Question -1

1. A car moves with an average speed of 75 km h from town P to town Q in 2 hours as shown in Figure 1. By using this information, you ma y calculate the distance between the two towns. P Q

Figure 1 (a) (i) Based on the statements given, state two basic quantities and their respective SI units. Distance : m and time : s ……………………………………………………………………………………… (ii) State a derived quantity and its SI unit. -1 Speed – m s ………………………………………………………………………………………

(b) Convert the value

1 . m to standard form. -3 5 x 10

= 0.2 x 10 m 2 = 2.0 x 10 m

(c) Complete Table 1 by writing the value of each given prefix.

-9

10

-6

10

6

10

9

10

Table 1 (d) Power is defined as the rate of change of work done. Derive the unit for power in terms of its basic units. kgms −2 × m work Force × displacement 2 -3 Power =

time

=

Unit =

time

s

= kg m s

(e) Calculate the volume of a wooden block with dimension of 7 cm, 5 cm breadth and 12 3 cm height in m and convert its value in standard form. -2

-2

-2

Volume = (7 x 10 ) (5 x 10 ) (12 x 10 ) -6 = 420 x 10 -4 3 = 4.20 x 10 m

17


2. Figure 2 shows an ammeter of 0—3 A range.

Figure 2 Mirror (a) (i) Name component X. ………………………………………………………………... To avoid parallax error (ii) What is the function of X? ………………………………………………………….

(b) Table 2 shows three current readings obtained by three students.

Table 2 No (i) Did all the students use the ammeter in Figure2? ..…………………………………. (ii) Explain your answer in (b)(i). rd 3 readings obtained by student 2 and 3 are out of the meter range. ………………………………………………………………………………………

3. Figure 3 shows the meniscus of water in a measuring cylinder K, L, and M are three eye positions while measuring the volume of the water. (a) (i) Which of the eye positions is correct while taking the reading of the volume of water? L …….……………………………………

Figure 3 (b) The water in the measuring cylinder is 3 replaced with 30 cm of mercury. (i) In Figure 4, draw the meniscus of the mercury in the measuring cylinder. Figure 4 (ii) Explain why the shape of the meniscus of mercury is as drawn in (b)(i). The cohesive force is larger than the adhesive force ………………………………………………………………………………………

18

Chapter 1 Introduction to Physics Teacher's Guide 2009

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