Work and Energy numericals Class 9 CBSE

1. A force of 10N causes a displacement or 2m in a body in its own direction. Calculate the work done by force. 20j) 2. How much force is applied on the body when 10joule of work is done in displacin! the body throu!h a distance of 10m in the direction of force"#1 N) $. A body of k! raised to 2m %nd the work done#&'j) (. A work of (&00j is done on road of mass 0 k! to lift it to a certain hei!ht. Calculate the hei!ht throu!h which the load is lifted. #10m) . An en!ine work (000* work by e+ertin! a force of ,000N on it. -hat is the displacement of the force . #10m) ,. A force of 10N actin! on a body at an an!le of ,00 with the horiontal direction displaces the body throu!h a distance dist ance of 2m alon! the surface of a /oor /o or.. Calculate the work done. Now let the force or pullin! act on the body makes an an!le of $00 with the horiontal. -hat is the alue of the force to displace the body throu!h 2m alon! the surface of the /oor" #Cos,0 12.Cos $0 3$2 ans. 10 * .4' N) 4. A force of N actin! on body at an!le of $00with the horiontal direction displace it horiontally throu!h of distance of , m . Calculate the work done. #13$ *) '. A body of mass 2k! is moin! with a speed of 20ms 5ind the kinetic ener!y. ener!y. #(00*) &. A moin! body of $0k! has ,0 * of 67. Calculate the speed. 10. A hammer of mass 1k! falls freely from a hei!ht of 2 m .Calculate #8) 9he elocity and #88) 9he ke. :f the hammer just before it touches the !round. ;oes the elocity of hammer depend on the mass of hammer" #,.2,m<2  1&., * ) 11. Calculate the ener!y posses by a stone of mass 10k! kept at a hei!ht of m 8f 1&,+102 * of ener!y were used to raise a (0k! boy aboe the !round how hi!h would he be raised" #0m) 12. Calculate the chan!e that should be a=ected in the elocity of a body to maintain the same 67  if mass of the body is increased to ( times #half the ori!inal elocity) 1$. A machine does 1&2 * of work in 2(0>ec. -hat is the power of the machine" #'w) 1(. A wei!htin! 0k! runs up a hill risin! himself ertically 10m in 20>ec. Calculate power. power. !ien !&.'m<1 #2(w)

1. A rickshaw puller pulls the rickshaw by applyin! a force of 100 N. 8f the rickaw moes with constant elocity of $, kmh<1. 5ind the power of rickshaw puller. #1000w) 1,. A athlete wei!hin! ,0k! runs up a staircase hain! 10 steps each of 1m in $0 sec. Calculate power #!'.'ms<1 200-) 14. 9he heart does 1. * of work in each heartbeat. How many times per minute does it beat if its power is 2watt" #'0 times) hint? total work p + t 120*  number times heartbeat in 1 min. total work done  work done in each beat1201.'0 times 1'. Calculate the time taken ,0 w bulb to consume $000 * of ener!y . #0sec. ) 1&. A horse e+ert a force of 200N to pull the cart. 8f the horse cart system moes with elocity $,kmh<1 on the leel road. then %nd the power of horse in term of horse power #1hp4(,-) Ans. 2.,'h.p 20. An electric kettle of 00- is used to heat water eeryday for 2 hours . Calculate the number of unit of electrical ener!y consumed y it in 10 days. #AN>. 10 @N89) 21. Calculate the cost of usin! a 2kwh immersion rod for heatin! water in a house for one hour each day for ,0 days if the rate is s. 1.0 per unit k-h. #s. 1'0) 22. How many unit of ener!y will be consume by a 100 - refri!erator in $0 days  if it works for 1, hrs. 7ery day. B('k-h#unit) 2$. A 1000w oen is used eeryday for &0 min. Calculate the unit of electrical ener!y oen consume in $0days. #( unit.) 2(. 9he power of a heart which beats 42 times in a minute is 1.2k-. Calculate the work done by heart for each beat. # 1k*)