Question

A force F doubles the length of wire having cross-section a. The Young modulus of wire is

• A. $\frac{F}{a}$
• B. $\frac{F}{3a}$
• C. $\frac{F}{2a}$
• D. $\frac{F}{4a}$

Answer 1

The correct option is A $\frac{F}{a}$

Young modulus,

$Y=\frac{F/a}{\Delta l/l}$.. . . . . . . . . . .(1)

As, $\Delta l=2l-l=l$

$\frac{\Delta l}{l}=1$

From equation (1),

$Y=\frac{F}{a}$

The correct option is A.