The angle between angular acceleration and angular velocity can vary depending on the specific scenario. However, if angular velocity is said to be decreasing, it implies that the angular acceleration is acting in the opposite direction of the angular velocity. In such cases, the angle between angular acceleration and angular velocity is generally 180 degrees (or π radians), indicating they are in opposite directions.
To illustrate this, consider a scenario where an object is rotating counterclockwise with an initial angular velocity. If the angular velocity is decreasing, it means that the object is slowing down. The angular acceleration, in this case, is acting in the clockwise direction, opposing the counterclockwise motion of the object. As a result, the angle between the angular acceleration and angular velocity would be 180 degrees (or π radians).
However, it's important to note that the specific angle between angular acceleration and angular velocity can vary in different situations, depending on the direction and magnitude of the angular acceleration and angular velocity.