Question

A girl having a mass of 35 kg sits on trolley of mass 5 kg. A trolley is given initial velocity of 4m/s by applying force. the trolley comes to rest after travelling a distance of 16 m. how much work done on trolley ? how much work is done by girl.?

Answer 1

Here, it is given that, mass of the girl = 35 kg and mass of the trolly = 5 kg
So, total mass m = 35+5 = 40 kg
Initial velocity, u = 4 m/s
Final velocity, v = 0
Distance, s = 16 m
Using the third equation of motion as,
v²= u² + 2as
or, 0 = 4² + 2a ⨉ 16
or, 32a = - 16
or, a = - 0.5 m/s²
Force exerted on trolly, F = ma = 40 ⨉ 0.5 = 20 N
Force exerted by girl, F = ma = 35⨉0.5 = 17.5 N
Now, work done on trolly, W = Fs = 20 ⨉ 16 = 320 J
And, work done by the girl, W = Fs = 17.5⨉16 = 280 J