# Homework Help: Radial component of linear acceleration

1. Mar 4, 2009

### Hotsuma

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

A 66-cm-diameter wheel accelerates uniformly about its center from 120 rpm to 260 rpm rpm in 4.9 s.

2. Relevant equations

$a_t = r\alpha$
$a_c= r\omega^2$
$a= a_r+a_t$

3. The attempt at a solution

I have discovered that:
$\alpha = 3.0 \frac{rad}{s^2}$
and
$a_t = 0.99/frac{m}{s^2}$

I have tried using Pythagoras's theorem to solve for $a_r$, but that value does not work. What am I doing wrong?

2. Mar 4, 2009

### Hotsuma

Oh, and I am using Mastering Physics and only have one submission left, so I had better make it count!

3. Mar 4, 2009

### Hotsuma

Anyone have an idea for this one?

4. Mar 4, 2009

### LowlyPion

What is the question?

Have you considered the rotational analogues to linear kinematic motion?

http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#rlin

5. Mar 4, 2009

6. Mar 4, 2009

### LowlyPion

At what point?

a = ω²r

So that means it is simply ω dependent.

Are you sure they don't want α - angular acceleration?

7. Mar 4, 2009

### Hotsuma

Well I've tried that and that value didn't work. The time limit is over I took a hit on that one. The answer they resulted in was 110 m/s. Whoa.