If you have a mass attached to a spring and it's hanging down vertically?

The only forces on it is gravity, which is pulling it down and the force of the spring in the opposite direction. How do the forces change if you pull the spring down and then let go so that the mass-spring system oscillates?If you have a mass attached to a spring and it's hanging down vertically?
This is essentially the classic harmonic oscillator. If you're looking for the differential equation treatment of the system check out http://en.wikipedia.org/wiki/Harmonic_os



Qualitatively, it's like this: When you pull the mass down, the restoring force becomes greater than gravity, so when you release the mass it accelerates upward. Once it passes the point of equilibrium (halfway through it's range of motion) gravity becomes the dominant force and the mass accelerates downward. This continues indefinitely since there is no friction.If you have a mass attached to a spring and it's hanging down vertically?
When you pull the mass down, you are building up potential energy in the spring. When you release, this turns into kinetic energy as the spring contracts. Gravity, which is still acting on the mass/spring, then pull the mass/spring down. The force of the mass/spring moving downwards causes the spring to stretch past its resting state and potential energy is built up again. The process repeats until the mass/spring is at rest.