1. An Indian rubber cord L metre long and area of cross-section

1. An Indian rubber cord L metre long and area of cross-section A metre ²  is suspended vertically. Density of rubber is D Kg/metre ³ and Young’s modulus of rubber is E newton/metre 2  . If the wire extends by l metre under its own weight, then extension l is

(a)    L² Dg/E                                          (b)  L² Dg/2E

(c)  L² Dg/4E                                          (d)   L

Answer-b