Q. A particular force (F) applied on a wire increases its length by $2 \times 10^{- 3}m.$ To increase the wire’s length by $4 \times 10^{- 3}m$ the applied force will be

A) 4 F
B) 3 F
C) 2 F
D) F
Explanation

(c) $Y = \frac{\frac{F}{A}}{\frac{l}{L}} = \frac{F \times L}{A \times l}$
(where Y is Young’s modulus of elasticity Since, Y, L and A remain same.
$F \propto l$
$\frac{F_{1}}{F_{2}} = \frac{l_{1}}{l_{2}}$
⟹ $\frac{F}{F_{2}} = \frac{2 \times 10^{- 3}}{4 \times 10^{- 3}}$
$F_{2} = 2F$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.