posted by zoya on .
A car of mass 1000kg moving with a velocity of 36km/h hits a wall and comes to rest in 5s.find the force and work done by the car on the wall.
36 km/h = 36000m/3600 s = 10 m/s
Car's initial momentum = 10^3*10
= 10^4 kg*m/s
Divide that by the stopping time (5 s) to get the average force, in newtons.
The "work done by the car" is the initial kinetic energy of the car,
(1/2)MVo^2 = 5*10^4 J,
but it is mostly converted to heat and inelastic damage distortion of the wall and the car itself.