Abstract: A general discussion of kinetic energy and elastic potential energy of springs in series is made on the occasion that the mass of spring can not be neglected. It turns out that kinetic energy of springs in series is not only related to spring mass ml, m2, but also spring constant kl ,k2, however, elastic potential energy is only decided by absolute elongation of springs in series and their elastic constants.

Key words: energy, springs in series, spring oscillator, spring mass