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Homework Help: Calculating force for a mass in a hoop

  1. Oct 17, 2011 #1
    1. The problem statement, all variables and given/known data
    A mass M of 6.40E-1 kg slides inside a hoop of radius R=1.60 m with negligible friction. When M is at the top, it has a speed of 5.25 m/s. Calculate the size of the force with which the M pushes on the hoop when M is at an angle of 37.0°.

    [URL]http://loncapa.gwu.edu/res/msu/physicslib/msuphysicslib/13_EnergyConservation/graphics/prob25_1015hoop2.gif[/URL]

    2. Relevant equations
    Finding the F


    3. The attempt at a solution

    i tried 2 times and both are wrong

    first i tried

    a=v^2/r
    a=(5.25)^2/1.6
    a=17.227

    F=ma
    F=(.640)(17.227)
    F=11.025N and thats wrong...

    second try i draw force diagram and got

    tan(37)=opposite/adjacent
    tan(37)mg=opposite
    4.726N=the horizontal force of the gravity? and its wrong.
     
    Last edited by a moderator: Apr 26, 2017
  2. jcsd
  3. Oct 18, 2011 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You're using the speed at the top. But you need the speed at 37°. Figure that out first.

    (FYI: Your diagram is not viewable.)
     
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