A wheel is set spinning and then is hung by a rope placed at one end of the axle. The precession vector of the spinning wheel points in the direction of
A) z
B) -y
C) -z
D) -x
E) y

Question

A wheel is set spinning and then is hung by a rope placed at one end of the axle. The precession vector of the spinning wheel points in the direction of 
A) z 
B) -y 
C) -z 
D) -x 
E) y

Quizplus · Accepted Answer

When a spinning wheel is hung by a rope placed at one end of the axle, the precession vector points in the direction opposite to the direction of the gravitational force acting on the wheel. This direction can be determined by applying the right-hand rule.

If the right-hand rule is applied with the thumb pointing in the direction of the spin axis (z-axis) and the fingers curling in the direction of the gravitational force (towards the center of the Earth), then the direction of the precession vector (which is perpendicular to the spin axis and the gravitational force) would be in the -z direction.

Therefore, the best choice is C) -z.

A Wheel Is Set Spinning and Then Is Hung by a Rope