# Simple Harmonc Motion

1. Oct 18, 2005

### enclosed

the question is
An object is undergoing simple harmonic motion with period T_1 and amplitude A. At t = 0 the object is at x = 0. How far is the object from the equilibrium position at time t?

well i come up with:
A*cos((2*pi/T_1)*t)

but i get that theres something wrong with my trigonometry, i cant figure out what im doing wrong

2. Oct 18, 2005

### ZapperZ

Staff Emeritus
Hint: if you substitute t=0, do you get x=0 with that cosine function?

Zz.

Last edited by a moderator: May 19, 2013
3. Oct 18, 2005

### Just some guy

Well as the object is at the equilibrium position at t = 0 there's no phase shift and the displacement is modelled as x = Asin(wt)

The period (let's just call it T for now) = 2pi/w, therefore w = 2pi/T

The equation for the displacement at time t then comes to x = Asin(2*pi*t/T), so unless I'm mistaken you just misread the initial conditions (if you wanted to make it into a cos expression you could give it a phase shift of pi/2).

Cheers,
Just some guy

4. Oct 18, 2005

### enclosed

OMG thanks so much, i noticed the mistake, hehe, its pretty late, should be sleeping not prepping for my upcoming middies..
Thanks guys for quick replies!