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. How much work is done on the trolley?

• A. 320 J
• B. 450 J
• C. 180 J
• D. 600 J

Answer 1

The correct option is A 320 J

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$=0m{s}^{-1}$
distance s$=$16m
we know,
$v^2-u^2=2as$
$a=\frac{v^2-u^2}{2s}$
$=-\frac{16}{2\times 16}$
$a=-\frac{1}{2}m{s}^{-2}$
Force$=ma=40\times (-0.5)$
$=$-20N
work is done on the trolley$=20N\times 16m=320$ J.
work was done by the girl $=$0 J.