As amassoscillates on a spring, so do the potential and kinetic energy, while their sum (mechanical energy)保持不变。

In the case of a horizontal spring:

• The points of maximumdisplacement从平衡位置(the turning points) are the points where the massvelocityis zero, and so is the kinetic energy. Here the energy is all potential energy stored in the deformation of the spring.
• At the平衡位置, however, the potential energy of the spring is zero (the spring is at its natural unstretched length) and the energy is all kinetic.

The situation is conceptually slightly different for a vertical spring. Here the potential energy is the sum of gravitational and elastic energy. However, if one measures the displacement from the 'new' mass equilibrium position (and not from the unloaded spring equilibrium position), the same considerations as the horizontal case apply.