A uniform wire of length $L$ and radius $r$ is twisted by an angle $\alpha$. If modulus of rigidity of the wire is $\eta$, then the elastic potential energy stored in wire, is .........
$\frac{\pi \eta r^4 \alpha}{2 L^2}$
$\frac{\pi \eta r^4 \alpha}{4 L^2}$
$\frac{\pi \eta r^4 \alpha^2}{4 L}$
$\frac{\pi \eta r^4 \alpha^2}{2 L}$
The ratio of Young's modulus of the material of two wires is $2 : 3.$ If the same stress is applied on both, then the ratio of elastic energy per unit volume will be
A stone of mass $20\, {g}$ is projected from a rubber catapult of length $0.1\, {m}$ and area of cross section $10^{-6} \,{m}^{2}$ stretched by an amount $0.04\, {m}$. The velocity of the projected stone is $....\,m\,/s.$ (Young's modulus of rubber $=0.5 \times 10^{9}\, {N} / {m}^{2}$ )
One end of a slack wire (Young's modulus $Y$, length $L$ and cross-sectional area $A$ ) is clamped to a rigid wall and the other end to a block (mass $m$ ), which rests on a smooth horizontal plane. The block is set in motion with a speed $v$. What is the maximum distance, then the block will travel after the wire becomes taut?
The work per unit volume to stretch the length by $1\%$ of a wire with cross sectional area of $1\,m{m^2}$ will be. $[Y = 9 \times {10^{11}}\,N/{m^2}]$
If $x$ longitudinal strain is produced in a wire of Young's modulus $y,$ then energy stored in the material of the wire per unit volume is