A steel wire 2 mm is diameter is just stretched between two fixed points at a temperature of `20^(@)C`. If the temperature falls to `10^(@)C`, then the tension in the wire is (Coefficient of linear expansion of steel `(alpha)` is `11xx10^(-6)//""^(@)C and Y_(s)=2.1xx10^(11)N//m^(2)`)

Options

A. 98.56 N
B. 725 N
C. 72.6 N
D. `7.25 xx 10^(3)N`

Answer

C

Explanation

`F=yA prop Delta t`
`=2.1 xx 10^(11) xx pi r^(2) prop Delta t`
`= 2.1 xx 10^(11) xx (22)/(7) xx 10^(-6) xx 11 xx10^(-6) xx 10`
`=0.3xx22xx11`
`=6.6xx11`
`=72.6N`.