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)

› Category: Questions › 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)
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Editor">Editor Staff asked 1 year ago

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
Select the correct answer from above options 
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Editor">Editor Staff answered 1 year ago

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 =
∫
2
0
(2x * g)dx
 
 =
∫
2
0
20xdx
 
 = 40 J.

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