# Homework Help: Angular Acceleration

Tags:
1. May 3, 2016

### oliampian

1. The problem statement, all variables and given/known data

This is not really a question on how to solve the problem, I'm just trying to get clarification on something. For angular acceleration, α, can someone explain to me what αz is? And why does αz = α / R = αy? I understand the rest of the problem, I just don't understand where or what αz is and how αz = α / R = αy. Thanks in advance for any help given!

2. May 3, 2016

### TSny

$\alpha_z$ apparently represents the angular acceleration for rotation about the z-axis.
The print in the picture is small and hard to read. In equation (2) I think it states that $\alpha_z = \large \frac{a}{R}$, not $\alpha_z = \large \frac{\alpha}{R}.$

3. May 3, 2016

### oliampian

Ohhh, you're right about the a/R not α/R. But can you explain to me why does a/R = ay?

4. May 3, 2016

### TSny

They aren't claiming that a/R = ay.

The R cancels: (1/2)MR(a/R) = (1/2)May. The "a" on the left is the same as ay.

5. May 3, 2016

### oliampian

Ok I see. And just to clarify, if I divide a linear acceleration by the radius R then we get angular acceleration?

Nvm! Figured it out. Thank yoooou! :)

Last edited: May 3, 2016