Angular Acceleration problem

  • Thread starter BrainMan
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  • #1
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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 = ωo + [itex]\alpha[/itex]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
 

Answers and Replies

  • #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?
 
  • #3
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2
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
 
  • #4
Nathanael
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2 pi

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

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