The heavy spring at work
  Springs are used in simple demonstrations for the students of Physics classes to illustrate the Hooke's Law and harmonic oscillations. The spring is usually considered as a light object that does not possess a mass. What happens if the spring is heavy, that is, if its mass is not negligible? This paper aims to discuss this problem as plainly as possible. 
Amelia Carolina Sparavigna
physics.pop-ph