Question

As shown in figure a person is pulling a mass $m$ from ground on a fixed rough hemispherical surface up to the top of the hemispherical surface with the help of a light inextensible string. The radius of hemisphere is $R$ and friction co-efficient between surfaces is $\mu$. Assume that the block is pulled with negligible velocity, the work done by tension in string is

• A. $mgR\left(1+\mu \right)$
• B. $mgR\left(\sqrt{2}+\mu \right)$
• C. $\mu mgR$
• D. $\sqrt{2}\mu mgR$

Answer 1

The correct option is A $mgR\left(1+\mu \right)$

Since the block is being pulled very slowly, its change in K.E. is zero.

$W_{net}=\Delta K.E.$

$W_T+W_{gr}+W_{fr}=0$

$W_T=mgR+\mu mgR$