Question

A chain of mass M is placed on a smooth table with 1/n of its length hanging over the edge. The work done in pulling the hanging portion of the chain back to the surface of the table is:

• A. (MgL)/(n)
• B. (MgL)/(2n)
• C. (MgL)/(n²)
• D. (MgL)/(2n²)

Hint:

Work done against gravity equals increase in gravitational potential energy.

Answer 1

The Correct Option is D

Step 1: Mass of hanging part, (M)/(n)
Step 2: Centre of mass of hanging part lies at (L)/(2n).
Step 3: Work done equals gain in potential energy, W = (M)/(n) g · (L)/(2n) = (MgL)/(2n²)