Question

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

(a) 84J

(b) 48J

(c) 24J

(d) 8J

The question was asked in exam.

The question is from Harmonic Motion topic in chapter Oscillations of Engineering Physics I

Answer 1

Right answer is (d) 8J

For explanation: k=F/x=10N/1mm=10N/(10^-3m)=(10^4)N/m

Work done in stretching the spring through 40mm,

W=1/2×kx^2=1/2×10^4×0.04×0.04=8J.