Question

Two wires are made of the same material and have the same volume. The area of cross sections of the first and the second wires are A and 2A respectively. If the length of the first wire is increased by ∆l on applying a force F, how much force is needed to stretch the second wire by the same amount?

(a) 2 

(b) 4 

(c) 8

(d) 16

Answer 1

(b) 4

Since the two wires have same volume 

Length of wire 1 = l, Area of wire 1 = A 

Length of wire 2 = \(\frac{l}{2}\) , Area of wire 2 = 2A