Question

A spring 40 mm long is stretched by the application of a force. If 10 N force required to stretch the spring through 1 mm, then work done in stretching the spring through 40 mm is

• A. 84 J
• B. 68 J
• C. 23 J
• D. 8 J

Answer 1

The correct option is D

8 J

Here $k=\frac{F}{x}=\frac{10}{1\times {10}^{-3}}={10}^{4}N/m$

$w=\frac{1}{2}k{x}^2=\frac{1}{2}\times {10}^4\times (40\times {10}^{-3}{)}^2=8J$