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 Displacement and Velocity

  1. Feb 5, 2009 #1
    1. The problem statement, all variables and given/known data
    A person is riding a bicycle, and its wheels have an angular velocity of +22.0 rad/s. Then, the brakes are applied and the bike is brought to a uniform stop. During braking, the angular displacement of each wheel is +11.0 revolutions.

    (a) How much time does it take for the bike to come to rest?
    s

    (b) What is the angular acceleration of each wheel?
    rad/s2


    2. Relevant equations
    theta = (angular velocity)(time)


    3. The attempt at a solution
    11=22t
    11/22 = t=1/2

    thats wrong i guess.
    can you help me out?
     
  2. jcsd
  3. Feb 5, 2009 #2

    AEM

    User Avatar

    Here's an interesting thing: The kinematic equations for rotational motion (be sure to use radians) have the same form as those for straight line motion:

    [tex] X = X_o + V_o t + \frac{1}{2} a t^2 [/tex]

    becomes

    [tex] \theta = \theta_o + \omega_o t + \frac{1}{2} \alpha t^2 [/tex]

    and so on. Therefore you can use many of the same ideas that you would use for straight line motion problems with simple rotational kinematics. For example, you could use

    [tex] \omega^2 = \omega_o^2 + 2 \alpha(\theta - \theta_o) [/tex]

    to find the angular acceleration in your problem above. I'll leave it to you to figure out the other parts.

    [tex] \omega [/tex] is the angular velocity; [tex] \alpha [/tex] is the angular acceleration in the above equations.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook