Engineering Board Exam Reviewer · Applications: Centroid, Work, and Moment of Inertia · easy

A spring has a natural length of 0.30 m, and a force of 40 N holds it stretched 0.10 m beyond natural length. How much work, in joules, is needed to stretch it from a length of 0.35 m to 0.50 m?

  1. 4.5
  2. 8
  3. 7.5
  4. 15

Answer

C. 7.5

Solution

k=40/0.10=400 N/m. The stretches are 0.05 m and 0.20 m. W= 0.050.20400x,dx=200≤ft(0.202-0.052 )=7.5 J.

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