Question

A chain of length 4 m is kept on a table. 2 m of the chain hangs freely from the table’s edge. The mass of the whole chain is 8 kg. What is the work done to pull the whole chain onto the table? (Assume g = 10m/s^2)

(a) 20 J

(b) 40 J

(c) 60 J

(d) 80 J

I have been asked this question in class test.

This key question is from Work Done by a Variable Force in chapter Work, Energy and Power of Physics – Class 11

Answer 1

Correct answer is (b) 40 J

The best I can explain: Mass per length of chain (p) = 8/4 = 2 kg/m

Mass of ‘x’ m of length = 2x kg

Force = \(\int_{0}^{2}\)(2x * g)dx

 = \(\int_{0}^{2}\)20xdx

 = 40 J.