1. Limited time only! Sign up for a free 30min personal 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!

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


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    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]?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook