Question

A force of ${10}^3$ newton stretches the length of a hanging wire by 1 millimetre. The force required to stretch a wire of same material and length but having four times the diameter by 1 millimetre is

• A. 4 X 10³ N
• B. 16 x 10³ N
• C.
• D.

Answer 1

The correct option is B 16 x 10³ N

(c) $F=Y\times A\times \frac{l}{L}\Rightarrow F\propto r^2$
(Y,l and L are constant)
If diameter is made four times then force required will be 16 times.i.e $16\times {10}^{3}N$