Simplify the following text for a Grade 9 native English-speaking person.
Original: It is sometimes also called the rotational velocity and its magnitude the rotational speed , typically measured in cycles or rotations per unit time ( e.g. revolutions per minute ) .
Simplified: When it is measured in cycles or rotations per unit time ( e.g. revolutions per minute ) , it is often called the rotational velocity and its magnitude the rotational speed .