Simple Harmonic Motion Phase angle

1. Aug 28, 2011

Jimmy84

1. The problem statement, all variables and given/known data
What is the initial phase angle of this graph that describes a simple harmonic motion?

2. Relevant equations

3. The attempt at a solution

I dont have any clue about how to find it by watching the graph, I know only an equation to find it. Any help please.

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Last edited: Aug 28, 2011
2. Aug 28, 2011

PeterO

I did a quick google search for "phase angle of shm" and the first site offered gave a good lead ... equation 510.
Any of the other offereings may have been just as useful.
Many were to other questions about phase angle here on Physics Forums in fact.

3. Aug 28, 2011

Jimmy84

Do you mean this http://farside.ph.utexas.edu/teaching/301/lectures/node138.html ? I already read them but i just started reading the theory about Simple Harmonic Motion yesterday and im a bit lost with it so is there any way to find the angle just by inspection of the graph? I didnt understand much of the previous posts about the subject on the forum

4. Aug 28, 2011

PeterO

That's the one.

I was particularly taken by the sentence before equation :

"Finally, the phase angle phi determines the times at which the oscillation attains its maximum amplitude, x=a: in fact"

If the phase angle was zero, then maximum amplitude would be happening then - so the graph of displacement vs time must look like a Cosine gragh.

A phase angle will translate the graph. Your graph is certainly translated. can you see by how much?