# Homework Help: Annoying Spring Problem

1. Apr 21, 2005

### ninjagowoowoo

Q:
A mass of 1.64 kg stretches a vertical spring 0.300 m. If the spring is stretched an additional 0.123 m and released, how long does it take to reach the (new) equilibrium position again?

What I tried:
Found k using F=kx (mg=kx)
using that k, I calculated the force in the extended spring (F=k(0.123))
using that force, I calculated the acceleration of the mass (F=ma)
finally, using x=(1/2)at^2 I calculated t.

I must be missing something obvious b/c this doesnt seem like a difficult problem...

2. Apr 21, 2005

### dextercioby

Nope,it's incorrect.The motion is not with constant acceleration.U need to find the period of vibration.

Daniel.

3. Apr 21, 2005

### ninjagowoowoo

Yeah thats what I thought....

So I calculated k in the first step above.
Then I used omega = sqrt(k/m) to get omega.
Then I used f = omega/2pi
Then period = 1/f and it's still wrong. Any other mistakes I made?

Thanks for the help

4. Apr 21, 2005

### dextercioby

Yes,the time required is only 1/4-th of the period...Can u see why?

Daniel.

5. Apr 21, 2005

### ninjagowoowoo

Wow hey thanks a lot. I guess brain just isn't working today.