Ball on a rotating inclined plane

[EllaRuth]

Homework Statement

A ball rests against the screw on the end of an inclined plane (θ = 33 °) which
rotates about a vertical axis. The center of mass of the sphere is in the horizontal distance r = 20 cm from the center of rotation to the inclined plane.

The inclined plane started to rotate with large angular speed, so that
the ball is held up by the end support. The angular velocity will then
become gradually lower due to friction.

1) Draw all the forces acting on the ball immediately after the inclined plane begins to rotate.
2) Determine the angular velocity of the inclined plane as the ball begins to roll.
3) What happens to the angular velocity of the inclined plane when the ball rolls down?

Relevant Equations

Conservation of angular momentum? Newtons 2nd law,

I have problems to even start with this exercise.

 

[kuruman]

Hi Ella Ruth and welcome to PF.

According to our rules, before you can get help you must show an effort to answer the question and tell us what you think. Surely you can draw all the forces acting on the ball and post your drawing.

 

[EllaRuth]

Hi Ella Ruth and welcome to PF.

According to our rules, you must show an effort to answer the question and tell us what you think before you can get help.

But I need help to start. I am extremely confused.

In 1) I'm sure to use G force and normal force, but I am not sure which force holds the ball up? I was told that sentrifugal force is not a real force, so I am not sure whether I can draw that. Sadly this is the only one I can think of.

In 2) I thought of using angular momentum, but then again it am not sure how to connect it with the rotation of the whole system,because angular momentum is not conserved (or at least I understand so since there is this friction force)

3. The system should spin faster again, because inertia changes and more mass is located close to the axis of rotation?

I am not great at physics and many of those concepts are totally abstract to me. If the ramp wasn't moving, I could easily solve this exercise. Here I am a bit hopeless.

 

[haruspex]

In 1) I'm sure to use G force and normal force, but I am not sure which force holds the ball up? I was told that sentrifugal force is not a real force, so I am not sure whether I can draw that.

Which frame of reference you use is your choice.

In the lab frame, there is no centrifugal force, but there is centripetal acceleration. So the only forces are gravity and the normal forces from objects the ball is in contact with. What are those objects?
The forces will not be in balance since the net force supplies the centripetal acceleration.

In the frame of reference of the rotating plane, the ball is not accelerating, so the forces on it must be in balance. In this frame there is a centrifugal force.

Since you appear to be a beginner with such problems, I recommend you to use the lab frame.