Question

A force is applied on a car of mass 1500kg ,so that its speed increases from 54km/h to 72km /h .Find the work done by the force on a car .

Answer 1

hi there,
mass=1500kg
initial velocity=54 km/h=15m/s
final velocity=72 km/h=20m/s
initial kinetic energy=1/2m u^2=1/2*1500*225=168750 j
final kinetic energy=1/2*mu^2=1/2*1500*400=300000 j
therefore work =300000-168750=131250 j.
i hope this helps u....

Answer 2

By Work Energy Theorem,

Change in Kinetic Energy=Work done= 1/2 mv² - 1/2 mu²

m=1500 kg
u=54km/h= 54*5/18= 15 m/s
v=72km/h=72*5/18= 20 m/s

W= 1/2 mv²-1/2 mu²
   = 1/2*1500*20² - 1/2*1500*15²
   = 750*400 - 750*225
   =750(400-225)
   =750*175
   = 131250 J
 W  = 131.250 KJ