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Circular Motion and speed of mass

  1. Oct 19, 2006 #1
    A mass m moves in a horizontal circle of radiuss r inside a frictionless cone of angle 2t. Determine the speed of the mass.

    I drew the free body diagram for the mass. Normal force points toward the center in the same direction as the acceleration. Gravity points down.

    x) N = m*v^2/r

    I don't know why, but gravity is the only force acting in the vertical direction. There is nothing to balance it out.

    I know that I will need to use the angle 2t somehow, but I don't know what to do.
  2. jcsd
  3. Oct 19, 2006 #2


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    The NET force will point in the same direction as the acceleration (that's from Newton's 2nd law). The normal force will point normal (perpendicular) to the surface of the cone and thus slightly upwards.
  4. Oct 19, 2006 #3
    Yes, thats right. Remember by definition normal force is wel, NORMAL to the surface. You should be able to find it easily now. Weight leads to normal, normal leads to net.
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