# Rotational Motion

1. Apr 28, 2012

### freshbox

Hi guys, I have a few doubts on Rotational Motion and hope someone can help me out.

This 3 formula is for finding angular velocity, angular acceleration and angular displacement right?
ω=ωi+αt
ω²=ωi²+2αδ
δ=ωit+1/2αt²

And this 3 formula is for finding the linear velocity/acceleration/displacement in a angular shape?
s=rδ
v=rω
α=rα

Thanks.

2. Apr 28, 2012

### ZxcvbnM2000

If you have no problems on linear acceleration then then only thing that changes in rotational motion is that u becomes ω , a becomes α , x becomes θ .

3. Apr 28, 2012

### freshbox

Thank you ZxcvbnM2000 for the reply.

I want to ask can I use this equation v=rω to find the angular velocity as well?

4. Apr 28, 2012

### ZxcvbnM2000

yes of course as long as you know the linear velocity and the radius ;p

5. Apr 28, 2012

### freshbox

Ok thank you for the explanation and help.

Out of topic abit, if a rock is thrown downward from the top of a building, the velocity I can set it as -ve or +ve, and usually people set it to +ve for the working to be easier, am I right?

6. Apr 29, 2012

### tiny-tim

hi freshbox!
only for constant acceleration (just like the linear case)
s=rδ works only for constant ω

the other two always work
yes, so long as you're careful to adjust the sign of g to match

7. May 1, 2012

### freshbox

thank you tiny-tim for the explanation.