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Homework Help: A problem on circular motion.

  1. Nov 30, 2009 #1
    1. The problem statement, all variables and given/known data
    A small object of mass 0.3 kg is moving inside a hemispherical bowl. It's angular velocity is 10 rad/s. The object travels in a horizontal circular path of radius 20 cm. Find the reaction on the object caused by the bowl and the radius if the bowl.

    2. Relevant equations
    Equations of circular motion..

    3. The attempt at a solution
    I tried resolving the reactions into two different directions. First, in the vertical direction. Because there is no acceleration in the vertical direction, F sin a (where a is the angle between the line of action of the reaction and the horizontal plane) is equal to the weight of the object (0.3 x g).

    So F sin a = 0.3 x g

    I did the same thing in the horizontal direction using F = ma. ( F = m x centripetal acceleration)

    F cos a = 0.3 x w2 x 0.20.

    However, I can't get beyond this. How can I find the reaction on the object?
    (I don't think you're allowed to give g a numerical value such as 10 or 9.8 )
  2. jcsd
  3. Nov 30, 2009 #2


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    Homework Helper

    You know both the horizontal and vertical component of the reaction force. How do you get the magnitude and the direction of this force then?

  4. Nov 30, 2009 #3
    You have two equations and two unknowns(Fand a)and you can treat these as simultaneous equations.One way is to divide equation one by equation two,the F will cancel and you will be left with an equation giving tan a(sin/cos=tan)
  5. Nov 30, 2009 #4
    OK.. thanks
    I did try dividing them. I seems I made a mistake in the simplification.
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