# Why they don't give me the same answer? dynamics of uniform circular motion

## Homework Statement

So a body $m$ is on a uniform circular motion ($\omega = d\theta/dt = \text{constant}$), it is suspended by an inextensible rope with negligeable mass

## Homework Equations

P = mg , didnt know what to put here

## The Attempt at a Solution

So this is what the book did.

What I did I drew the same diagram on another way so I an use polar coordinates (second picture)

So the Weight is perpendicular to the vector $r$ and $\theta$, this is a problem since we won't have $mg$ in our equation at the end like the reasoning with the other picture but lets continue. On r:

$$- T \sin \alpha = -rw^2$$

on $\theta$:

$$-T \cos \alpha = 0$$

And this is wrong.

I've been confused for 3 days in a row , what am I doing wrong?

[1]: http://i.stack.imgur.com/FntS7.png
[/B]

Second picture is he same system but from uppoint of view , it gives me diffrent results

DEvens