# Homework Help: Springs problem.

1. Nov 4, 2012

### vysero

A mass of 10kg hangs from an ideal (massless) spring from the ceiling. The mass and spring are in static equilibrium, so there is no motion. If the spring has a spring constant k=1000N/m and g = 10 m/s/s, what is the (potential) energy stored in the spring?

PE = mgh and KE(of spring)= 1/2kx^2 and maybe hooks law

Kind of stumped.

I am not sure how to go about this problem as I am not sure if it is a trick question. Since PE = mgh and there is no height here would the PE = 0? If I set PE = 1/2kx^2 I have one equation with two unknowns which does not help me. I want to say its a conservation of energy problem but I am not sure. Please help me understand.

2. Nov 5, 2012

### haruspex

It asks for the PE stored in the spring, not gravitational PE.
But you do need to work out the spring extension.

3. Nov 5, 2012

### vysero

Ah okay so:

100N = 1000(x), x = .1

and (1/2)(1000)(.1)^2= 5 joules, is that right?

4. Nov 5, 2012

Looks right.