# Homework Help: *Simple frequency and period question - Thanks!

1. Jan 9, 2012

### nukeman

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

Ok, below is the question. I am having trouble with getting started. Like the first steps. A and B are the questions im having trouble with.

"A 1.00 kg glider attached to a spring with a force constant of 25.0 N/m oscillates on a frictionless, horizontal air track. At t = 0, the glider is passing through its equilibrium position with a velocity vx = - 0.150 m/s. (The negative sign means that the glider is headed in the direction which will compress the spring.)

(a) Calculate the frequency and period of the glider’s motion.

(b) Calculate the amplitude of the simple harmonic motion. "

2. Relevant equations

3. The attempt at a solution

EDIT: This is from my notes

Frequency = 1/T
Where T = Period
Or Period = 1/f
Where f is Frequency

But im not sure how to get the answer to A) for this question from that above data. ?

is this correct for period?

2*pi*sqrt( 1/25) = 1.25

so frequency would be 1 / 1.25 = .8?

NOW, is this correct for B) amplitude:

KE = PE, so answer I got was when solving for x was: .03

Last edited: Jan 9, 2012
2. Jan 10, 2012

### JHamm

You should have a formula for the period of a mass on a spring somewhere in your notes.

3. Jan 10, 2012

### cupid.callin

For time you may use time period of SHM
viz $T = 2\pi \Large{\sqrt{\frac{m}{k}}}$

EDIT:

To find this, consider eqn for x coordinate of SHM, $x=Asin(\omega t + \delta)$

This x repeats itself when sin repeats, ie, after 2π or time period T

$sin(\omega t + \delta + 2\pi) = sin(\omega (t+T) + \delta)$

$(\omega t + \delta + 2\pi) = (\omega (t+T) + \delta)$

$T = \Large{\frac{2\pi}{\omega}}$ and in starting of this derivation we assume $\omega = \Large{ \sqrt{\frac{k}{m}} }$

Last edited: Jan 10, 2012
4. Jan 10, 2012

### nukeman

I am very lost on this. Is anything I did correct?

Any help would be fantastic to get me started. Thanks!