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Homework Help: Which way would the tricycle go?

  1. Jul 21, 2009 #1
    Hello! my first post here

    This is more of a conceptual question.

    Assume normal friction in this type of situation, when pulling on the specific pedal (shown in pic) what happens to the tricycle (move backwards, forwards?) Also assume the steering is locked.

    What are 4 concepts in physics that explain this?

    We were having a discussion about this in class and no one agreed, so now it's homework....

    I believe given friction under these circumstances it should roll back.
    As for the 4 concepts in physics, my ideas so far are 1.) torque 2.) angular momentum. Any more then id be guessing.


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    Last edited: Jul 21, 2009
  2. jcsd
  3. Jul 22, 2009 #2
    Last edited by a moderator: Apr 24, 2017
  4. Jul 22, 2009 #3
    Hi Mark. :smile:

    Welcome to physicsforums! I'm relatively new here too, so I hope to see you around.

    For your question, try this. For a moment, forget that you have a bicycle or whatever, simply take a look at what forces are acting on your object. I see, for one, an external tension force pulling on the front. If a force is pulling on the front, then how can the bicycle, or any object for that matter, move backwards? Don't worry about angular momentum, torque, rotation, etc. Just think of Newton's second law for translational motion.
  5. Jul 23, 2009 #4


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    As previously said it will help to forget most of the trike. Look at just the wheel and treat it as a circle. You're applying a moment to the center, you have friction.

    Draw your free body diagram correctly and make sure to label your forces in the proper direction and it should be apparent.
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