Final answer:
Positive angular acceleration is conventionally associated with counterclockwise rotation. Angular velocity increases in the counterclockwise direction are positive, while a slowdown in that direction results in negative angular acceleration.
Step-by-step explanation:
In physics, the conventional direction for positive angular acceleration is counterclockwise. When an object rotates counterclockwise, its angular velocity vector is directed out of the plane, following the right-hand rule. This is considered the positive direction for rotational motion. Conversely, clockwise rotation corresponds to negative angular acceleration because the angular velocity vector would be directed into the plane.
Whether an object's angular acceleration is positive or negative depends on its change in angular velocity over time, as well as the orientation of the rotation. According to convention, if an object increases its rotation rate counterclockwise, its angular acceleration is positive. However, if an object rotating counterclockwise starts to slow down, the angular acceleration is negative because it opposes the initial direction.
Understanding the direction of angular velocity and acceleration is crucial in rotational motion problems, especially when applying the right-hand rule to determine vector directions within a coordinate system.