Question

A girl having mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of $4m{s}^{-1}$ by applying a force. The trolley comes to rest after traversing a distance of 16 m. (a) How much work is done on the trolley? (b) How much work is done by the girl?

Answer 1

a) Work done on the trolley
mass of girl m=35kg
mass of trolley=5kg
total mass=40kg
initial velocity of trolley $u=4m{s}^{-1}$
final velocity of trolley $v=0$
distance $s=16m$

We know that
$a=\frac{v^2-u^2}{2s}=-\frac{16}{2\times 16}=-\frac{1}{2}m{s}^{-2}$
$Force=ma=40\times (-\frac{1}{2})=-20N$
Work done on the trolley $=20N\times 16m=320J$

b) Work done by the girl = 0J.