Question

The force required to stretch a wire of cross-section $1 cm ^2$ to double its length will be:
(Given Yong's modulus of the wire $=2 \times 10^{11} N / m ^2$ )

• A. $1 \times 10^7 N$
• B. $1.5 \times 10^7 N$
• C. $2 \times 10^7 N$
• D. $2.5 \times 10^7 N$

Answer 1

Answer: (C)

$ F =\gamma A \frac{\Delta \ell}{\ell} $
$ =2 \times 10^{11} \times 10^{-4}\left(\frac{2 \ell-\ell}{\ell}\right) $
$ =2 \times 10^7 N $