# Relationship between harmonic and circular motions

1. Apr 21, 2015

### Calpalned

1. The problem statement, all variables and given/known data
How is $\frac{v}{v_M} = \frac{\sqrt{A^2 - x^2 }}{A}$ derived?

2. Relevant equations
n/a

3. The attempt at a solution
I don't see a right angle in the picture anywhere, so I don't see how pythagorean's theorem is valid.

2. Apr 21, 2015

### SammyS

Staff Emeritus
I see three.

What do v and vm represent?

3. Apr 22, 2015

### Calpalned

Ok, I see where $\sqrt{A^2-x^2}$ came from. However, why are $v_m = A$ and $v=\sqrt{A^2-x^2}$? According to the picture, shouldn't $v=x$?

Last edited: Apr 22, 2015
4. Apr 22, 2015

### Calpalned

Why did the textbook choose to do $\frac{v}{v_M}$?

5. Apr 22, 2015

### SammyS

Staff Emeritus
What is it that v and vm represent? What is the context of this figure and the quantities shown in it ?