Net/Everyday Forces

Question

You hang a spring from a tree and measure its length to be 1.0m. You suspend 15kg from the spring and i stretches to a new length of 1.4m. Find the spring constant for this spring.

Answer 1

The restorative force of the spring is proportional to the change from equilibrium, i.e. F=kΔx, and this must equal the weight of the mass placed on it, so

kΔx=mg, which when solved for k, we get k=mg/Δx,

or

k=(15 kg)(9.81 m/s²)/(1.4m-1.0m)=370 N/m (2 sig figs)