How Do You Calculate Average Angular Acceleration from Revolutions?

[BrainMan]

Homework Statement

A turntable moves from rest to an angular speed of 45 rev/min in 1.5 s. What is its average angular acceleration?

Homework Equations

ω = ω_o + $\alpha$t

The Attempt at a Solution

I first converted 45 to radians by multiplying it by pi
45(3.14152654)/180 = .79 rad
then I plugged it into the above equation
.79 = α(1.5)
α = .53 r/s²
The actual answer is pi r/s²

 

[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?

 

[BrainMan]

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?

2 pi

 

[Nathanael]

2 pi

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

 

[Nathanael]

I first converted 45 to radians by multiplying it by pi
45(3.14152654)/180 = .79 rad

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