A massless spring with spring constant 27.7 N/m hangs vertically. A body of mass 0.31 kg is attached to its free end and then released. Assume that the spring was unstretched before the body was released. How far below the initial position does the body descend?
F = kx
The Attempt at a Solution
I realized that the weight is the force so I set kx = mg, however I was told that in actuality the equation should be 2mg = kx, so my question is why is it 2mg? I don't get it.