Q. A stress of $3.18 \times 10^{8}Nm^{- 2}$ is applied to a steel rod of length $1m$ along its length. Its Young’s modulus is $2 \times 10^{11}Nm^{- 2}$. Then the elongation produced in the rod in $mm$ is

A) 3.18
B) 6.36
C) 5.18
D) 1.59
Explanation

(d) $Y = \frac{F/A}{\mathrm{\Delta}l/l}$
Given, $F/A =$ stress $= 3.18 \times 10^{8}Nm^{- 2}$
$l = 1m,\ Y = 2 \times 10^{11}Nm^{- 2}$
$\mathrm{\Delta}l = \frac{lF/A}{Y} = \frac{1 \times 3.18 \times 10^{8}}{2 \times 10^{11}} = 1.59 \times 10^{- 3}m = 1.59mm$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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