# Spring to the top

**Classical Mechanics**Level 4

A heavy mass is attached to a spring of natural length \(8~\mbox{m}\) and spring constant \(k=100~\mbox{N/m}\). The top of the spring is attached to a ceiling, which is \(10~\mbox{m}\) above the mass. The mass is then pulled horizontally for a distance of \(10~\mbox{m}\) and released. It therefore slides back along the ground towards where it started. What is the kinetic energy of the mass **in Joules** when it returns to its starting point?

**Details and assumptions**

- The floor is frictionless.
- The mass is heavy enough that it always rests on the ground.
- Treat the mass as a point mass.