Question

A light inextensible string that goes over a smooth fixed pulley as shown in the figure connects two blocks of masses 0.36 kg and 0.72 kg. Talking g= ${ms}^{-2}$, find the work done (in joule) by string on the block of mass 0.36 kg during the first second after the system is released from rest

• A. $8J$
• B. $9J$
• C. $7J$
• D. $0.48J$

Answer 1

The correct option is A $8J$

$\begin{array}{c}2mg-T=2ma\\ T-mg=ma\\ \Rightarrow a=\frac{g}{3}\\ T=\frac{4mg}{3m}\\ W=T.s=T\left[\frac{1}{2}a{t}^2\right]\\ =8J\end{array}$

Hence,

Option $A$ is correct.