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Angular Acceleration problem

  1. Jun 6, 2014 #1
    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 + [itex]\alpha[/itex]t


    3. 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
     
  2. jcsd
  3. Jun 6, 2014 #2

    Nathanael

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    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?
     
  4. Jun 6, 2014 #3
    2 pi
     
  5. Jun 6, 2014 #4

    Nathanael

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    So if I have [itex]45\frac{rev}{min}[/itex] how many [itex]\frac{radians}{min}[/itex] will it be?
     
  6. Jun 6, 2014 #5

    Nathanael

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