# Homework Help: Forces, marble on side of spinning bowl

1. Mar 22, 2013

### bang

1. The problem statement, all variables and given/known data
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

2. Relevant equations
I guess F=ma
a=v^2/r
Ff=Fnμ

3. The attempt at a solution
No idea how to start even approaching this, sum of all forces?

Last edited: Mar 22, 2013
2. Mar 22, 2013

### MostlyHarmless

It would probably help us to see the figure stated in the problem.

Looks like you've got a centripetal force problem.

3. Mar 22, 2013

### bang

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.

4. Mar 22, 2013

### bang

I put a picture up now.

5. Mar 22, 2013

### haruspex

Draw a free body diagram for the marble. As functions of theta, what forces act on it? What is the resultant force for equilibrium?