What is an angular momentum and what is its SI unit?

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BlackTom AI · Accepted Answer

To tackle the question, I will examine what angular momentum means and what its SI unit should be.
Option a: 'The angular motion of a moment of inertia, the unit is kg.m2/s2' This statement incorrectly pairs angular motion with a moment of inertia and also gives the unit kg·m^2/s^2, which is actually the unit of torque or energy (depending on context), not angular momentum. The phrasing is imprecise and misleads about the relationship between inertia and angular motion.
Option b: 'The moment of inertia of an object moving at a constant angular velocity, the unit is rad/s' Here, the statement confuses a property (moment of inertia) with a description of the motion; it also lists the unit rad/s, which is an angular velocity unit, not angular momentum. The concept and the unit do not match.
Option c: 'The momentum of an object moving in rotational motion, the unit is kg.m2/s' This aligns with the standard definition of angular momentum: L is the rotational analog of linear momentum, defined for a body in rotational motion. The typical expression L = I ω or L = r × p leads to SI units of kilogram square meters per second (kg·m^2/s), which matches the unit given. This description correctly captures both the concept and the unit.
Option d: 'The angle of an object moving at a constant momentum, the unit is kg.m/s' This mixes angular measure (angle) with momentum and assigns an incorrect unit (kg·m/s is linear momentum; also angle is not a momentum measure). The idea conflates angular quantity with a non-rotational parameter, making it inaccurate.
Overall, only option c correctly describes angular momentum as the momentum associated with rotational motion and assigns the proper SI unit, kg·m^2/s, while the other options either misdefine the concept or provide inconsistent units.

UCIC 202503 PHYS101 Quiz 5

What is an angular momentum and what is its SI unit?

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