What force would be required to stretch a streel wire fo `4 mm^2` cross section, so that its length becomes 3 times its original length ? Given that Young's modulus of the meterial of the steel wire is `2.4 xx 10^(12) dyne // cm^2.`

Answer

`1.92 xx 10^(11) dyn e`

Explanation

Here `F =?, A = 4 mm^2 =4xx10^(-2) cm^2 ,` increase in length `Delta l = 3l - l = 2l,`
`Y = 2.4 xx 10^(12) dyn e//cm^2`
As `Y = (F)/(A) (l)/(Delta l)`
or `F = (YA Delta l)/(l) = ((2.4 xx10^(12))xx(4xx10^(-2))xx2l)/(l)`
`(2.4 xx 4xx2xx10^(10)`
`=19.2 xx10^(10) = 1.92 xx 10^(11) dyn e`