Question

a body of weight mg is hanging on string which extends in length by l the work done in extending the string is a) mgl b) mgl/2 c) 2mgl d) none of the above​

Answer 1

The work done in extending the string is mgL.

Explanation:

We are given:

L = h  

• The gravitational force is a conservative field.  
• The work done by the body to extend the string is equivalent to  the potential energy of the body.

As we know that

Potential Energy P.E  = mgh

Here H  = L so,

Potential Energy P.E  = mgL

Thus the work done in extending the string is mgL.

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