Answer: 
Explanation:
Given
Cross-sectional area of wire 
Extension of wire 
Extension in a wire is given by

where, 

for same force, length and material

Divide (i) and (ii)

True. it’s at rest which means it’s not moving so there’s no acceleration
When someone stands against a locker and is does not moving at all, then there will be no displacement and since displacement = 0
Work done also becomes equal to zero.
Work done is usually defined as change in energy. Since the work done is zero there has been no energy used.
Gravitational energy is a form of potential energy because it is dependent on the mass of an object and needs to be calculated for the specific object.
The answer is 0.025J.
W=1/2*k*x^2
W=1/2*20*0.050^2
W=0.025J