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Rotational Mechanics

  1. Nov 23, 2009 #1
    A motor rotating at 60rpm comes to rest in 10 revolutions with its angular velocity decreasing linearly with angular displacement.Determine it angular velocity as a function of time and determine angular velocity w at t=3 sec..


    I need help with this problem...Please someone help...I cant do anything in rotational mechanics:(
     
  2. jcsd
  3. Nov 23, 2009 #2

    cepheid

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    Hi Pratz, welcome to PF!

    To get you started, you know the that the angular velocity is a linearly decreasing function of angular displacement, meaning that:

    [tex] \omega(\theta) = \omega_0 - C\theta [/tex] ​

    You know what the inital angular velocity, [itex] \omega_0 [/itex] is, because it is given in the problem. You can calculate the constant by noting that the angular velocity equals zero after ten revolutions: [itex] \omega(10 \textfm{rev}) = 0 [/itex]. Remember to convert everything into radians. Now that you have this function [itex] \omega(\theta) [/itex], you can differentiate it with respect to theta. Can you think of a way of relating that to the time derivative of [itex] \omega[/itex]?
     
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