# Calculate the magnitude of angular acceleration

## Homework Statement

A record player rotates normally at a rate of 18 rev/m.
It takes 70 seconds for it to slow down to a stop when you turn it off.

## Homework Equations

Calculate the magnitude of its angular acceleration.

## The Attempt at a Solution

gneill
Mentor
Hi reformedman, Welcome to Physics Forums.

You've stated what needs to be found in the Relevant equations section of the template. That's not a relevant equation, it's part of the problem statement. So what equations do you know that might apply to this type of problem?

What have you tried?

phyzguy
You need to make an attempt to solve the problem before we can help. What do you know about angular velocity and angular acceleration?

it's been 30 years since college and I was just browsing the net when I found that familiar problem. I seem to recall something about 2 pi related to rads somehow. I'm not really pressed for the solution, was just wondering. Glad I found this forum though, looking around a bit.

gneill
Mentor
it's been 30 years since college and I was just browsing the net when I found that familiar problem. I seem to recall something about 2 pi related to rads somehow. I'm not really pressed for the solution, was just wondering. Glad I found this forum though, looking around a bit.
Well, if you want to solve the problem it looks like you'll need to review the basics. There are plenty of resources on the web if you search the appropriate terms. You'll be looking for kinematic equations related to angular motion (or rotational kinematics). They're of the same form as those for linear motion (look up: SUVAT), but use angular quantities rather than linear ones.

it's been 30 years since college and I was just browsing the net when I found that familiar problem. I seem to recall something about 2 pi related to rads somehow. I'm not really pressed for the solution, was just wondering. Glad I found this forum though, looking around a bit.

Don't over think this one. If this were linear motion and I gave you a starting speed and said it took 70 seconds to stop under constant deceleration would you know how to calculate the deceleration?

Also, the reason you are getting cagey suggestions instead of answers is because this is a "homework" forum. There are also non- homework forums. However this looks like a homework problem so you would probably have to swear vehemently that this isn't homework in order to get a straight answer.