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!

Loop the loop

  1. Aug 3, 2009 #1
    1. The problem statement, all variables and given/known data
    A cyllinder of radius rc starts a height h above a loop the loop on a track. If the radius of the loop is rl, how high does h need to be. The cyllinder does not slip. Express the answer in terms of the radius of the loop.


    2. Relevant equations

    Conservation of energy

    3. The attempt at a solution

    The cyllinder has potential energy mgh at the beginning and 2mgrl at the top of the loop. It also has kinetic energy 1/2mv^2 +1/2Iw^2 where v=[tex]\sqrt{rg}[/tex] is the critical velocity. The moment of inertia is I = 1/2mrc^2. I cant figure out how to get rid of rc in the answer.

    I get h = rl/2 + rc^2/4rl + 2rl
     
  2. jcsd
  3. Aug 3, 2009 #2

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    To do what, exactly? Can you clarify what the problem is asking, and what it means when it says that the cylinder starts at height h "above" the loop?
     
  4. Aug 3, 2009 #3

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi clarineterr! :smile:

    (try using the X2 and X2 tags just above the Reply box :wink:)
    I can't see how you got that :confused:

    can you give us some detail?

    (and it isn't 2mgrl at the top … don't you need to subtract some rc?)
     
  5. Aug 3, 2009 #4
    Im sorry. How high must h be for the cyllinder to be able to go around the loop.

    At the top of the loop the only centripetal force is gravity if the cyllinder just makes it around the loop so v=[tex]\sqrt{grl}[/tex]

    then I used mgh = 1/2mv^2 + 1/2Iw^2 + 2mgrl and if you v/r for w, the moment of inertia and the velocity above mg cancels out.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Loop the loop
  1. Loop the Loop problem (Replies: 0)

  2. Loop the loop (Replies: 1)

  3. Loop the Loop (Replies: 10)

  4. Loop a loop (Replies: 4)

Loading...