Forces, marble on side of spinning bowl

AI Thread Summary
The discussion revolves around a physics problem involving a marble in a spinning bowl with a hemispherical surface. The bowl has a radius of 15 cm and completes a rotation every 0.72 seconds. Participants suggest that the problem involves centripetal force and recommend drawing a free body diagram to analyze the forces acting on the marble. The angle θ is defined as the angle from a vertical line drawn from the bowl's center. The key focus is on determining the forces for equilibrium and how they relate to the angle θ.
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Homework Statement


A bowl has a hemispherical inside surface with radius R = 15
cm, and is sitting in the exact center of a spinning table that completes
one full turn in 0.72 s. A small marble is dropped into the bowl. After
the marble has stopped rolling around, it will come to rest against the
inside surface of the bowl, rotating around the center of the table at the
same rate as the bowl. You can ignore the size of the marble. The
angle θ, as defined in the figure, is closest to ___?

DIAGRAM SHOWING THE PROBLEM
http://imgur.com/0pKoAKT

Homework Equations


I guess F=ma
a=v^2/r
Ff=Fnμ

The Attempt at a Solution


No idea how to start even approaching this, sum of all forces?
 
Last edited:
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It would probably help us to see the figure stated in the problem.

Looks like you've got a centripetal force problem.
 
I don't really have access to a diagram, but basically its a semi-circle, with a marble resting on the side of the bowl. The angle theta is the angle from a line that is straight up from the center of the bowl.
 
I put a picture up now.
 
Draw a free body diagram for the marble. As functions of theta, what forces act on it? What is the resultant force for equilibrium?
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
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