Simple Harmonic Motion (easy question)

1. Aug 1, 2009

MarineBio

1. The problem statement, all variables and given/known data

A 0.26 kg mass attached to a spring undergoes simple harmonic motion with a period of 0.84 s. What is the force constant of the spring?

2. Relevant equations

T = 2*pi*SQRT(m/k)

3. The attempt at a solution

I know this is supposed to be an easy question, but for some reason I can't do it. Here is what I got (which is not right):

T = 2*pi*SQRT(m/k) and to solve for "k":

K = 2*pi*SQRT(m)[whole thing divided by .84 seconds] = 3.814 N/m

Ok, so what am I doing wrong? Thanks!

2. Aug 1, 2009

cepheid

Staff Emeritus
Your algebra doesn't look right. To solve for k, you want to get it by itself on one side of the equation, which involves:

1. Getting rid of the 2pi (by dividing both sides of the equation by 2pi).
2. Getting rid of the square root (by squaring both sides).
3. Getting k on top (taking the reciprocal of both sides)
4. Getting rid of the m (multiplying both sides by m)

3. Aug 1, 2009

nickmai123

It might make it more clear if it looked like this:

$$T=2\pi \sqrt{\frac{m}{k}}$$

Now solve for k.

HINT: Squaring both sides gets rid of the square root.

4. Aug 1, 2009

MarineBio

ok so K = (2*pi*m)/T^2

That gives me 2.315 N/m which is also incorrect. Hmm... I don't know.

5. Aug 1, 2009

Chrisas

You forgot to square the 2*Pi

6. Aug 1, 2009

MarineBio

Problem solved. Thank you