A change due to direction is a bit more difficult for students to visualize. For small angles of , is approximately equal to the arc length, s , on the imaginary circle. This is Newton's Second Law. Therefore, if an object is already spinning when a Net Torque is exerted on it, then the Net Torque will cause the Angular Momentum of the object to change. Depending upon the nature of the Net Torque, this change could be in the form of magnitude, direction, or both.
Precession is rotation about another axis.
As a result, there is a new angular velocity created, . If the rate of precession of the object is constant, then the magnitude of this new angular velocity is also constant. The Net Torque, the Angular Momentum of the Disk, and the Angular Speed of Precession of the Gyroscope are capable of being measured. In other words, the total angular momentum of the system does not change, even if individual parts of the system do. The purpose of Activity 2 is to use Conservation of Angular Momentum to determine the unknown magnitudes and directions of various momentum vectors when a person, initially at rest on a stool, turns a spinning bicycle wheel upside down.