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Calculate the magnitude of angular acceleration

  1. Dec 21, 2016 #1
    1. The problem statement, all variables and given/known data
    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.

    2. Relevant equations
    Calculate the magnitude of its angular acceleration.

    3. The attempt at a solution
    answer key says the correct answer should be .027 rad/s^2
     
  2. jcsd
  3. Dec 21, 2016 #2

    gneill

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    Staff: 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?
     
  4. Dec 21, 2016 #3

    phyzguy

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    Science Advisor

    You need to make an attempt to solve the problem before we can help. What do you know about angular velocity and angular acceleration?
     
  5. Dec 21, 2016 #4
    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.
     
  6. Dec 21, 2016 #5

    gneill

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    Staff: Mentor

    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.
     
  7. Dec 21, 2016 #6
    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.
     
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