Question

A stone of mass m is attached to one end of a wire of cross-sectional area A and young’s modulus Y. The stone is revolved in a horizontal circle at a speed such that the wire makes an angle $\theta$ with the vertical. The strain produced in the wire will be,

• A. $\frac{mgcos\theta }{AY}$
• B. $\frac{mg}{AYcos\theta }$
• C. $\frac{mgsin\theta }{AY}$
• D. $\frac{mg}{AYsin\theta }$

Answer 1

The correct option is B $\frac{mg}{AYcos\theta }$


$Tcos\theta =mg$
$\Rightarrow T=\frac{mg}{cos\theta }$
Increase in the length
Of wire is, $\Delta l=\frac{TL}{AY}$
Strain $=\frac{\Delta l}{L}=\frac{mg}{AYcos\theta }$