A wire elongates by `l` mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm)

Options

A. `l`
B. `2l`
C. `zero`
D. `l/2`

Answer

d

Explanation

Let us consider the length of wire as L and cross-sectional area A, the material of wire has Young's modulus as Y.

Case 1 `Y = (w//A)/(I//L)`
case 2 `Y = (w//A)/(2I'//L) :. I' = (1)/(2`
So, total elongation of both sides = 2I' = I