- #1

sapz

- 33

- 1

## Homework Statement

Hi

Im trying to solve this question, and I have the solution of it in front of me, but I really can't understand why its true.

The question is this: A bowl with radius R is given, it can't move. In it there's a ball with radius r << R, and a mass m.

Find... (lots of subclauses for the question)

A picture is attached.

My question is this:

Am I mixing the directions of the forces/torques?

F is the friction force.

**I think the torque equation should be I*w_dot=F*r**.

and the equation for the tangential direction should be ma=F-mgs*sin(theta).

**However**, in the solution I see here the torque equation appears with a minus sign: I*w_dot=-F*r, which obviously changes the answers of the things I need to find.

Should it be with a minus? Or without? Thank you.