Question

A particle of mass $10\text{kg}$ is dropped from tower of height $10\text{m}$. Find the ratio of workdone by gravity from point ${}^{\prime }{A}^{\prime }$ to ${}^{\prime }{B}^{\prime }$ and change in potential energy from ${}^{\prime }{A}^{\prime }$ to ${}^{\prime }{B}^{\prime }$

• A. $1$
• B. $-1$
• C. $2$
• D. $16$

Answer 1

The correct option is B $-1$

Work done by force of gravity from $A$ to $B$, $W_{AB}=\left(mg\right)h=mgh...\left(i\right)$
(Positve because force & displacement are in the same direction)

Change in potential energy from point $A$ to $B$,
$U_{AB}=U_B-U_A...\left(ii\right)$
$=mg(10-h)-mg\left(10\right)$
(calculating from ground as a reference)
$=-mgh$
$\therefore \frac{W_{AB}}{U_{AB}}=\frac{mgh}{-mgh}=-1$

Hence option B is the correct answer