A metal wire `4m` long and `2xx10^(-7)sq.m` in cross-section is stretched by a force of `30N`. If the work done in stretching that wire is `4.5xx10^(-2)J` the young's modulus of the wire is

Options

A. `2xx10^(11)N//m^(2)`
B. `4xx10^(11)N//m^(2)`
C. `2xx10^(12)N//m^(2)`
D. `4xx10^(12)N//m^(2)`

Answer

A

Explanation

`W=(1)/(2)F xx l`
`=(1)/(2)F xx (FL)/(Ay)`
`therefore y=(1)/(2) xx (30xx30xx4)/(2xx10^(-7)xx4.5xx10^(-2))`
`=2xx10^(11)N//m^(2)`