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!

Rotational Kinematics- sphere

  1. Apr 11, 2009 #1
    A solid sphere of uniform density starts from rest and rolls without slipping a distance of d = 4.2 m down a q = 26° incline. The sphere has a mass M = 5.1 kg and a radius R = 0.28 m.

    a) Of the total kinetic energy of the sphere, what fraction is translational?


    b) Suppose now that there is no frictional force between the sphere and the incline. Now, what is the translational kinetic energy of the sphere at the bottom of the incline?

    I figured out that KEtran is 65.8 j. I figured out that the phere reaches the bottom of the ramp at a speed of 5.08. the magnitude of friction forceon the sphere is 6.25 N. I just dont know what to do for a or b...any help?
     
  2. jcsd
  3. Apr 11, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    If there's no friction, what fraction of the total KE is translational?
     
  4. Apr 11, 2009 #3
    all?
     
  5. Apr 11, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Right. Without the torque due to friction, it will slide down the incline without rolling.
     
  6. Apr 11, 2009 #5
    ok so that would be for b. Im still kind of stuck on a.
     
  7. Apr 11, 2009 #6
    im confused on how to find the total kinetic energy
     
  8. Apr 11, 2009 #7

    Doc Al

    User Avatar

    Staff: Mentor

    Assuming that you posted the problem completely, for a you don't need to find the actual total energy, just the fraction that's translational. (Don't plug in any specific numbers.)

    Express the translational and rotational KE and see how they relate for a sphere rolling without slipping. Hint: How does ω relate to translational speed?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Rotational Kinematics- sphere
  1. Rotational Kinematics (Replies: 2)

Loading...