A metal wire of coefficient of linear expansion and Young modulus are `1xx10^(-5)//""^(@)C` and `10^(11)N//m^(2)` respectively is tied between two points rigidly at a temperature `40^(@)C`. If the temperature is decreased to `20^(@)C` the force required to hold the wire in newton is ( the length of the wire is 40 cm and area of cross section is `1 cm^(2)`)

Options

A. 20 N
B. 200 N
C. 2000 N
D. 1000 N

Answer

C

Explanation

`F=yA prop Delta t`
`=10^(11) xx 10^(-4) xx 10^(-5) xx (40 xx 20) =10^(2) xx 20`
`=2000N`.