# Homework Help: Angular Acceleration problem

1. Jun 6, 2014

### BrainMan

1. The problem statement, all variables and given/known data
A turntable moves from rest to an angular speed of 45 rev/min in 1.5 s. What is its average angular acceleration?

2. Relevant equations
ω = ωo + $\alpha$t

3. The attempt at a solution
I first converted 45 to radians by multiplying it by pi
then I plugged it into the above equation
.79 = α(1.5)
α = .53 r/s2
The actual answer is pi r/s2

2. Jun 6, 2014

### Nathanael

Your conversion is where the problem is. You want to convert from rev/min to rad/sec

First let's convert from rev/min to rad/min:

How many radians are in 1 revolution?

3. Jun 6, 2014

2 pi

4. Jun 6, 2014

### Nathanael

So if I have $45\frac{rev}{min}$ how many $\frac{radians}{min}$ will it be?

5. Jun 6, 2014

### Nathanael

That is how you convert 45 DEGREES into radians. But the number 45 has units of REVOLUTIONS, not degrees.