Question

A wire elongates by 8 mm when a load of 9 kg is suspended from it. What is the elongation when its radius is doubled, if all other quantites are the same as before ?

Answer 1

Correct Answer - 2 mm
`Y = (F)/(pi r^2). (l)/(Delta l) or r^2 Delta = (Fl)/(pi Y) =` a constant
Therefore, `r_1^2 Delta l_1 = r_2^2 Delta_2`
or `Delta_2 = ((r_1)/(r_2))^2 Delta l_1 = ((r )/(2r))^2xx8mm` = 2mm