# What is the direction of the red ball's angular momentum

SammyS
Staff Emeritus
Homework Helper
Gold Member
So is this a 3d image mapped into a 2d image and the vector labeled as "rA" is either pointed out from the page or into the page? The momentum vector is to the right, so maybe we assume the ball is rolling clockwise (rolling to the right), in which case the angular momentum vector should be into the page (right hand rule).
The ball is not rotating. The ball is not rolling. It's as if the ball is a point mass.

All motion is in the plane of the page, and the ball is at the location of the red dot. The big gray circular thing must just be some other object.

rcgldr
Homework Helper
All motion is in the plane of the page, and the ball is at the location of the red dot.
So effectively, A is the center of rotation, rA is the current position of the center of mass of the ball, and p/mass = velocity, so the rotation is counter-clockwise, and the direction of the angular momentum vector is out of the page.

mfb
Mentor
So effectively, A is the center of rotation, rA is the current position of the center of mass of the ball, and p/mass = velocity, so the rotation is counter-clockwise, and the direction of the angular momentum vector is out of the page.
Right.