At `40^(@)C` a brass wire of 1mm radius is hung from the ceiling. A small mass, M is hung from the free end of the wire. When the wire is cooled down from` 40^(@)C` to `20^(@)C` it regains its original length of 0.2 m the value of M is close to (coefficient of linear expansion and young's modulus of brass are `10^(-5)//.^(@)C` and `10^(11)//N//m^(2)` respectively `g=10ms^(-2))`

Options

A. 9 kg
B. 1.5 kg
C. 0.5 kg
D. 0.9 kg

Answer

A

Explanation

`y=("stress")/("stra in")=(F//A)/(Deltal//l)`
`y=(mg)/(AalphaDeltaT),m=(yAalphaDeltaT)/(g)=2pi`