Question

A string of area of cross-section $4mm^2$ and length $0.5 m$ is connected with a rigid body of mass $2 kg$. The body is rotated in a vertical circular path of radius $0.5 m$. The body acquires a speed of $5 m/s$ at the bottom of the circular path. Strain produced in the string when the body is at the bottom of the circle is ______$×10^{–5}$.

(use young’s modulus $10^{11} N/m^2$ and $g = 10 m/s^2$)

Answer 1

The correct answer is : 30

Strain = $F/AY$

$= \frac{mg + \frac{mv^2}{R}}{AY}$
$=\frac{ 20 + \frac{25^2}{0.5}}{4 × 10^{-6}× 10^{11} }= 30 × 10^{-5}$