Question

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

(a) 23J

(b) 68J

(c) 84J

(d) 8J

Answer 1

The correct answer is (d) 8J

The best explanation: Spring constant, k = F/x = 10N/1mm = 10N/(10^-3 m)= 10^4 N/m

Work done in stretching the spring through 40m,

W = 1/2 kx^2=1/2×10^4×(40×10^-3)^2 = 8J.