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Homework Help: Velocity needed to complete a loop

  1. Jun 5, 2008 #1
    1. The problem statement, all variables and given/known data
    Loop with radius 22m is all that is given and the required velocity to complete this loop is asked for.

    2. Relevant equations
    What I'm looking for.

    3. The attempt at a solution
    I've tried many equations, the answer is 33m/s but I don't know what equations to use to attain it.

    Any help with equations would be great,

  2. jcsd
  3. Jun 6, 2008 #2
    you need to use energy conservation. Take your initial energy before gettig into the loop and your final energy at the top of the loop. What is the condition that the object doesnt fall from the loop? You need to convert your initial kinetic energy into the gravitational potential at the top of the loop and the kinetic energy at the top which you will find from the condition that is required to keep the object from falling.
  4. Jun 6, 2008 #3


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    Hi Numzie! :smile:

    The question is rather vague, but I think you're meant to assume that it's an aeroplane, and it's powered, so it can have any velocity, v, that it wants.

    So what acceleration is needed to keep it in the circle?

    And what velocity is needed to produce that acceleration? :smile:
  5. Jun 6, 2008 #4

    Doc Al

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    Staff: Mentor

    You really should post the complete problem exactly as it was given to you.

    But given the answer that you provided, I suspect that the question is something like this: A cart enters the bottom of a loop. What speed must it have at the bottom to just barely complete the loop without falling off. (The cart is on the inside of the loop.)

    Assuming this is accurate, you'll need energy conservation (as stated by EngageEngage), but you'll also need to analyze the force and acceleration acting on the cart at the top of the loop (as tiny-tim suggests).
  6. Jun 6, 2008 #5


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    Yes, Doc Al and EngageEngage are right … it's an unpowered cart. :redface:

    The answer I get is 33 m/s.

    Show us what you've tried, and then we can help you.:smile:
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