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Homework Help: Find The Max Velocity (using coefficient of friction)

  1. Oct 25, 2011 #1
    1. The problem statement, all variables and given/known data

    If a mass of 609 kg travels in a circle with a radius of 102 m, and the μ= .13, and the acceleration of gravity is 9.8 m/s^2. What is the max velocity that the mass can go without canceling out the force of friction?

    2. Relevant equations


    3. The attempt at a solution

    I don't know I could really use some help!
  2. jcsd
  3. Oct 25, 2011 #2

    rude man

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    Must be horizontal motion (normal to circle is vertical).

    OK, then, what is meant by 'static friction'?
    Last edited: Oct 25, 2011
  4. Oct 25, 2011 #3
    static friction vs. kinetic friction. static being the force needed to get the object moving, and kinetic the force needed to keep the object in motion (always less then static)

    my biggest issue is finding the right combination of equations to use...

    any help?
  5. Oct 25, 2011 #4

    rude man

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    OK, so how much force can we apply to the mass before it starts to slide away from its circular path?

    (I hope you know the rules of this forum. We don't just do your work for you. If we did you'd learn nothing. We try to nudge you in the right direction and expect you to do your part as we go).
  6. Oct 26, 2011 #5
    Yes of course I know that! I understand the question completely I don't need any help interpreting it, the problems are very do-able, but as I said I need help on finding out the right equation to use since there are so many. Just a simple reference to the name of some equations would help... This particular homework was already due, but I'd still like to be able to solve it.

    I know since the mass is 609 kg, and the acceleration of gravity is 908 m/s^2 then the force of gravity on the mass is 5968.2 N, and I think that also means the force normal, is also 5968.2 N since those are the only two forces acting in the y direction.

    I also know that Force of friction = μ times the force normal, so I think I can use the above magnitude, but I'm not sure if that's right. Also, where does the velocity equation come in?
  7. Oct 26, 2011 #6

    rude man

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    Good. So the centripetal force is needed to keep the mass from flying tangentially off the table. And that force is provided by static friction. You already know that Fstatic friction = μW, do you know the formula for centripetal force, given m, v and r?
    Last edited: Oct 26, 2011
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