question_answer

A block of mass 1 kg is pulled along the curve path ACB by a tangential force as shown in figure. The work done by the frictional force when the block moves from A to B is

A) 5 J

B) 10 J

C) 20 J

D) None of these

Correct Answer: C

Solution :

[c] Work done by friction \[=\int{\vec{F}.\overrightarrow{ds}=\int\limits_{0}^{x}{\mu mg\cos \theta \frac{dx}{\cos \theta }=\mu mgx=20\,\operatorname{J}}}\]