If a rod of Young's modulus 20 G Pa undergoes a linear strain of `6xx10^(-4)`, then increase in its energy density will be

Options

A. `3600J//m^(3)`
B. `7200 J//m^(3)`
C. `1800 J//m^(3)`
D. `5400 J//m^(3)`

Answer

A

Explanation

`y=20xx10^(9)N//m^(2), (l)/(L)=6xx10^(-6)`,
`u=(1)/(2)y("strain")^(2)`
`=(1)/(2)xx20xx10^(9)xx(6xx10^(-4))^(2)`
`=10^(10) xx 36xx10^(-8)`
`=36xx10^(-2)J//m^(3).`