alleryStart learning →A torque acts on a spinning body. In which direction does its angular momentum change?
AIn the same direction as the torque
BOpposite to the direction of the torque
CAlong the original angular momentum
DAlways along the vertical direction
Answer & Solution
Correct answer: A. In the same direction as the torque
1. The vector form of the relation is net torque equals delta L divided by delta t.
2. Time is a positive scalar, so delta L must point the same way as the torque.
3. So the change in angular momentum lies along the torque, not along the existing L.
4. When the torque is perpendicular to L, the direction of L turns while its magnitude holds steady.
5. That perpendicular case is exactly what produces gyroscopic behaviour.
_Source: OpenStax College Physics (CC BY 4.0), Ch 10 "Rotational Motion and Angular Momentum", section 10.7 Gyroscopic Effects: Vector Aspects of Angular Momentum_
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