# Homework Help: Spring HW Question

1. Nov 17, 2004

### ccbb

I have a hw problem where a mass of 25kg hits a spring with a velocity of 10 m/s and compresses the spring 2.5m. The coefficent of friction between the object and the surface is .2. If someone could give me the starting point in finding the spring constant, and what velocity the object will have when the spring rebounds back to the equilibrium postion

2. Nov 17, 2004

### Sirus

I'm assuming you are dealing with a horizontal spring. Usually problems like these are best approached from an energy transfer perspective. Before the object hits the spring, the total energy in the system is just its kinetic energy, $E_{K}$. Then as the spring compresses, how is the energy transfered? Remember the work done by friction. This formula might be useful for determining the spring constant:
$$E_{elastic~potential}=\frac{1}{2}kx^2$$
where k is the spring constant, and x is the displacement from equilibrium.

Last edited: Nov 17, 2004