question_answer

A uniform chain of length L and mass M is lying on a smooth table and one third of its length is hanging vertically downward over the edge of table, if g is acceleration due to gravity, then the work done required to pull the hanging part on to the table is :

A) MgL                                      

B)  MgL/3

C)  MgL                                     

D)  MgL/18

Correct Answer: D

Solution :

                Weight of chain = Mg Weight of hanging part \[=\frac{Mg}{3}\] Displacement required to pull the chain \[=\frac{1}{2}\left( \frac{L}{3} \right)=\frac{L}{6}\] Work = force \[\times \]displacement