Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area A and wire 2 has cross-sectional area 3A. If the length of wire 1 increases by `Deltax` on applying force F, how much force is needed to stretch wire 2 by the same amount?

Options

A. `4 F`
B. `F`
C. `6 F`
D. `9 F`

Answer

D

Explanation

Since that wire have same volume,
`Al = 3 Al' implies l' = l//3`
`Delta l = (Fl)/(AY) = (F' (l//3))/(3 AY)`
`F' = 9 F`