1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Angular Acceleration!

  1. Oct 31, 2006 #1
    Question: A cooling fan is turned off when it is running at 850 rev/min. It turns 1500 revolutions before it comes to a stop.
    A. What is the fan's angular acceleration?
    B. How long does it take for the fan to come to a stop?

    I am pretty stumped with this question. I know that I have to use the equation a= omega (angular velocity)/ time ........and angular velocity= Change in theta/time ....but i am not sure how to go about the problem .......can anyone help?
  2. jcsd
  3. Oct 31, 2006 #2
    You said it: [tex] \alpha = \frac{\Delta \omega}{\Delta t}[/tex]
    Be careful though. 850rev/min is the frequency, NOT the angular velocity. But these are related by [tex] 2\pi f = \omega[/tex].
  4. Oct 31, 2006 #3
    thanks Euclid ..... so I got an angular velocity of 5340 rev/sec .......but how would I figure out the time since a= change in angular velocity/time
  5. Oct 31, 2006 #4
    i am really confused.... i dont even know if i got the angular velocity right ..... 5340 revolutions per second seems so much ....

  6. Oct 31, 2006 #5
    Firstly, angular velocity is in units of 1/s or rad/s, not rev/sec.

    Secondly, sorry for misleading you, I read the question wrong. You want to use the equation:

    [tex] 2 \alpha \Delta \theta = \omega_f^2 - \omega_i^2[/tex]

    How many radians does 1500 revolutions correspond to?
  7. Oct 31, 2006 #6
    would 1500 revolutions = 3000 radians? or am i totally off
  8. Oct 31, 2006 #7
    i know that the acceleration must be negative ..... considering wf=0 .... and -w1^squared= 2Atheta
  9. Oct 31, 2006 #8
    anyone there ?? please help!!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Angular Acceleration!
  1. Angular acceleration (Replies: 1)

  2. Angular acceleration! (Replies: 2)