# Homework Help: Oscillating in Simple Harmonic Motion?

1. Apr 24, 2012

### jisrael93

1. The problem statement, all variables and given/known data
A 200-g object is oscillating in simple harmonic monition with an amplitude of 2 cm and a period of 0.4 seconds. Find the velocity when its displacement from the equilibrium position is 0.5 cm.

2. Relevant equations
Restoring Force = -(constant force)(displacement)
Elastic PE = 1/2 k(s squared)
velocity = $\sqrt{k/m(A squared - s squared}$

3. The attempt at a solution
I just need help finding the constant force. If I can figure out how to solve that variable, I can finish the problem just fine.

2. Apr 24, 2012

### Staff: Mentor

I think you mean the "force constant", k, for the spring. Why not consider the formula for the period of a mass-spring system?

Also try using the x2 and x2 icons in the edit frame header to produce superscripts and subscripts

3. Apr 24, 2012

### azizlwl

I missed them too.
Hope they are repositioned at Quick Symbols and adding new symbol, 1/2.

Thank you.

4. Apr 24, 2012

### jisrael93

Thanks, I'm not sure how I missed that - I think the first part of this homework fried my brain before I got to this and I just forgot to look at my other equations! However, when I acquired a k value of 49.35 and did the equation in my original post for velocity, I acquired a negative number under the radical, therefore giving me a non-real answer. Am I doing something wrong?

5. Apr 24, 2012

### Staff: Mentor

Your value for k looks fine (you should include units when you present a number).

The equation you wrote for velocity is okay. Maybe finger problems on the calculator?
Why not show your calculation step by step?