# Homework Help: Little help in mass on a spring

1. Apr 21, 2012

### Akibarika

1. The problem statement, all variables and given/known data
a steel spring that it extends by 10cm in equilibrium when you attach the upper end of the spring to a fixed support and hang a weight of 100g at the lower end.

I want to know how to use the equation for the harmonic oscillator to determine the period of the up and down oscillation.

2. Relevant equations
F = -kx
F = ma

3. The attempt at a solution
I want to use F = ma and F = -kx
so ma = -kx
k = ma/-x
= 0.1*a/-0.1
= -a

but I don't know the a, is the a for 9.81? and maybe I was wrong in the beginning

Thanks a lot

2. Apr 21, 2012

### Staff: Mentor

Use Hooke's law (F = -kx) to find the spring constant. What force is exerted on the spring by the hanging mass?

3. Apr 21, 2012

### Akibarika

so I can use F = mg
=> mg = -kx ?

is that right?

4. Apr 21, 2012

### Staff: Mentor

Yes, that's how you can find the spring constant.

5. Apr 21, 2012

### Akibarika

thank you very much! cheers