Calculate the work done in streching a steel wire of Young's modulus of `2xx10^(11) Nm^(-2)` ,length of 200 cm and area of cross-section is 0.06 `cm^(2)` slowly applied without the elastic limit being reached.

Explanation

Here, force `F=mg=40xx9.8` kg
Length of wire, l=200 cm =2 m
Area of cross section, A`=0.06 cm^(2) = 0.06xx10^(-4) m^(2)`,
Young's modulus, `Y=2xx10^(11) Nm^(-2)`
Work done `=(1)/(2)` stretching force `xx` extension `=(1)/(2) Fdeltal`
`=(1)/(2)Fxx(Fl)/(AY)`
`W=(F^(2)l)/(2AY)=((40xx9.8)^(2)xx2)/(2xx0.6xx10^(-4)xx2xx10^(11))=0.128 J`