Question

a spring with a spring constant of 18.0 N/cm has attached to its free end .How much work does the spring force do on the cage when the spring is stretched from its relaxed length by (N+7.6)mm?

Answer 1

By the definition of the work done, we get:

$$W=\dfrac{1}{2}k(x_f^2-x_i^2),$$ $$W=\dfrac{1}{2}\cdot18\ \dfrac{N}{cm}\cdot\dfrac{100\ cm}{1\ m}\cdot(7.6\cdot10^{-3}\ m)^2=0.052\ J.$$