Circular motion and velocity of car

1. Apr 19, 2005

dalitwil

A conceptual question:

A car travels in a circular path with constant speed. Which of the following quantities is constant and non-zero for this car?

a.) linear velocity
b.) angular velocity
c.) centripetal acceleration
d.) angular acceleration
e.) total acceleration

The answer is b.) angular acceleration, but why? I figured it would have to be linear velocity, because ang velocity=v/r and isn't the r of a circular path going to be constant? So how can angular velocity be constant without the linear velocity constant?

2. Apr 19, 2005

OlderDan

I repaired what I assume is a typographical error in your post.

Linear velocity is a vector. If you change its direction, you have changed it. If you change its magnitude (speed) you have chaged it. If you change both, you have changed it. You can keep the magnitude of linear velocity constant in circular motion. The v in the definition of angular velocity means the magnitude of the linear velocity. More precisely, angular velocity is a vector perpendicular to the plane of motion. It is a vector product of linear velocity and a position vector. If you have never heard of that, don't worry about it now. Just remember that only the magnitude of v is needed to calculate the magnitude of angular velocity.