Certified Flight Instructor - Flight Instructor Airplane Practice Exam

With regard to gyroscopic precession, when a force is applied at a point on the rim of a spinning disc, the resultant force acts in which direction and at what point?

1. In the same direction as the applied force, 90° ahead in the plane of rotation.

2. In the opposite direction of the applied force, 90° ahead in the plane of rotation.

3. In the opposite direction of the applied force, at the point of the applied force.

4. At the point of the applied force, with no specific direction.

The correct answer is: In the same direction as the applied force, 90° ahead in the plane of rotation.

When a force is applied to a point on the rim of a spinning disc, gyroscopic precession dictates that the resultant force acts 90 degrees ahead in the plane of rotation. This phenomenon occurs due to the inertia of the spinning object and its angular momentum. When you apply a force to a gyroscope, instead of simply responding in the direction of the applied force, it creates a change in orientation that is manifest 90 degrees further along in the direction of spin. This behavior can be understood by considering the forces acting on the disc. When a torque is applied, the disc's angular momentum vector attempts to maintain its direction. The change occurs not in the direction of the applied force but rather in a direction perpendicular to it, resulting in the precession motion that is observed. This relationship is foundational in the operation of various aviation instruments, such as gyroscopic flight instruments, where understanding the direction of angular momentum is critical for accurate readings and control.