Gyroscopic Motion - I

For very small angle between initial and final vectors, the change will be perpendicular to the intial vector. Thus, change in the angular momentum is in the direction of negative z. Therefore,a torque in the vertical negative z-direction is needed. This is not present here, so the disk will not precess in vertical plane.

(Precise analysis will show that the disk will oscillate in the xz plane, and spin velocity is not a constant velocity, but should be understood as the mean velocity only.)

Before going into detail about the gyroscopic motion, I will first present simple examples of engineering importance concerning this topic.

Till now, we have understood

(1) If a body is spinning and a torque is applied normal to the axis of spin, the body starts precessing and the precession axis is normal to the axis of spin and axis of torque. The torque is often named a gyro-couple.