Question

A girl having mass 35 kg sits on a trolley of mass 5 kg.The trolley is given an initial velocity of 4m/S by applying a force. The trolley came to rest after travelling 16m.
a) How much work is done on trolley?
B) How much work is done by the girl?

Answer 1

Given:
Mass of girl = 35 kg
Mass of trolley = 5 kg
Total mass, m = (35 + 5) = 40 kg
 u = 4 m/s
v = 0
s = 16 m
By equation,
v 2 = u 2 + 2as
0 = (4)2 + 2a (16)
32a = –16
a = –0.5 m/s2
Force exerted on trolley,
F = ma
   = 40 × 0.5 = 20 N
 
Work done on trolley W = FS = 20 N x 16 m
                                                 = 320 J
Work done by the girl, W = FS
                                          = mass of girl × retardation × S
                                          = 35 × 0.5 × 16
                                          = 280 J