Question

A girl having a mass of $35kg$ sits on a trolley of mass $5kg$. 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 $16m$. How much work is done on the trolley?

• A. $0J$
• B. $320J$
• C. $120J$
• D. $250J$

Answer 1

The correct option is B $320J$

Given,

Mass of the girl, $m_g=35kg$

Mass of the trolley, $m_t=5kg$

Iniial velociy, $u=4m{s}^{-1}$

Final velocity, $v=0$

Displacement, $s=16m$

Total mass, $m=m_g+m_t$

$m=35+5=40kg$

Using Newton's second equation of motion,

$s=ut+\frac{1}{2}{u}^2$

$⟹a=\frac{v^2-u^2}{2s}$

$a=-\frac{0^2-4^2}{2\times 16}$

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

Force, $F=ma$

$F=40\times (-0.5)$

$F=-20N$

Magnitude of force, $F=20N$

Work done on the trolley, $W=(20\times 16)J$

$W=320J$