Question

A heavy block is suspended from a vertical string the elastic potential energy stored in the spring is 4J what is the spring constant if the elongation of the spring is 10cm?

Answer 1

We can find the spring constant from the definition of the elastic potential energy:

$$PE_s=\dfrac{1}{2}kx^2,$$ $$k=\dfrac{2PE_s}{x^2},$$ $$k=\dfrac{2\cdot4\ J}{(0.1\ m)^2}=800\ \dfrac{N}{m}.$$