Question Detail

PHY 101 Rigid Body Dynamics Objective Question
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Question

Under what condition is the angular momentum of a particle about a point zero, even if it has non-zero momentum?
Options
A When the particle is at rest.
B When the particle is moving in a circle centered on the point.
C When the position vector and the momentum vector are parallel or anti-parallel.
Correct Answer
D When the position vector and the momentum vector are perpendicular.
Correct Answer

Option C is the correct answer.

Detailed Explanation

The magnitude of angular momentum is L = r p sin θ. This becomes zero if sin θ = 0, which occurs when θ = 0° or 180°, meaning the vectors r and p are parallel or anti-parallel. In such a case, the particle is moving directly towards or away from the reference point, giving it no rotational effect about that point.

Hint

The angular momentum is the 'moment' of momentum, analogous to the moment of a force. When is the moment of a force about a point zero?

Question Info

Course: PHY 101
Topic: Rigid Body Dynamics
Type: Objective
Difficulty: Not specified
Question 644 of 1250
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