Question

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

• A. $0J$
• B. $320J$
• C. $280J$
• D. $100J$

Answer 1

The correct option is C $280J$

Mass of girl =$35kg$

Mass of trolley = $5kg$

Total Mass =$35+5=40kg$

$u=4m/s,v=0m/s,s=16m$

By 3rd equation of motion, $v^2=u^2+2as$

$0^2=4^2+2a\left(16\right)$

$a=-0.5m{s}^{-2}$

$\therefore$ force exerted on trolley=$40\times 0.5$

$=20N$

Work done on trolley = $20\times 16J$

$=320J$

Work done by the girl = $F.s$

$=M_{girl}\times retardation\times s$

$=35\times 0.5\times 16J$

$=280J$