Question

When is the positive sign used for the expression of gyroscopic couple?

(a) Centre of gravity is lower than the centre of vehicle

(b) When the engine is rotating in the opposite direction as that of wheels

(c) When the engine is rotating in the same direction as that of wheels

(d) Centre of gravity is higher than vehicle centre

I got this question in an online interview.

This intriguing question comes from Stability of a Two Wheel Vehicle Taking a Turn topic in portion Gyroscopic Couple and Precessional Motion of Machine Dynamics

Answer 1

The correct option is (c) When the engine is rotating in the same direction as that of wheels

To elaborate: To decide the direction of rotation between wheels and the engine, conventionally a positive sign represents the same direction and negative sign represents opposite direction.