If Young.s modulus of the material of a wire is `1.2xx10^(11) Nm^(-2)` , calculate the work done in stretching the wire of length 3 m and cross-sectional area `4mm^(2)` when it is suspended vertically and a load of 8 kg is attached to its lower end.

Explanation

`Y = 1.2 xx 10^11 Nm^(-2) , L = 3m, A = 4mm^2 = 4 xx 10^(-6) m^2 , M = 8 kg `
`Y = 1.2 xx 10^11 Nm^(-2) , L = 3m ` ,
`A = 4mm^2 = 4 xx 10^(-6) m^2 , M = 8 kg `
work done = 1/2 x stretching force x increase in length.
But increase in length, `e = (FL)/(AY)`
The work done ` = 1/2 xx (F^2L)/(AY) = 1/2 xx ((mg)^2L)/(AY)`
` = 1/2 xx ((8 xx 9.8)^2 xx 3)/(4 xx 10^(-6) xx 1.2 xx 10^11)`
` = 0.0192 J`