Angular momentum is a physical quantity that describes the rotational motion of an object around an axis or point. It is an important concept in physics, especially when studying rotating objects, planets, particles, and mechanical systems.
What Is the SI Unit of Angular Momentum?
The SI unit of angular momentum is kilogram meter squared per second (kg·m²/s).
It can be written as:
kg·m²/s
Angular momentum is commonly represented by the symbol L.
Angular Momentum Formula
The angular momentum of a rotating object can be calculated using:
L = Iω
where:
- L = angular momentum
- I = moment of inertia
- ω = angular velocity
The SI unit of moment of inertia is kg·m², while angular velocity is measured in rad/s. Therefore:
kg·m² × rad/s = kg·m²/s
Since the radian is dimensionless, the SI unit is kg·m²/s.
What Is Angular Momentum Measured In?
Angular momentum is measured in kilogram meters squared per second (kg·m²/s) in the International System of Units (SI).
For example, if an object has a moment of inertia of 2 kg·m² and an angular velocity of 5 rad/s:
L = 2 × 5 = 10 kg·m²/s
Therefore, the angular momentum is 10 kg·m²/s.
Is kg·m²/s the Same as J·s?
Yes. Angular momentum can also be expressed as joule-seconds (J·s).
This is because:
1 J = 1 kg·m²/s²
Therefore:
1 J·s = 1 kg·m²/s
So, both kg·m²/s and J·s represent the same physical unit.
Dimensions of Angular Momentum
The dimensional formula of angular momentum is:
[M L² T⁻¹]
where:
- M = mass
- L = length
- T = time
Angular Momentum vs. Linear Momentum
Angular momentum should not be confused with linear momentum.
| Quantity | SI Unit |
|---|---|
| Linear momentum | kg·m/s |
| Angular momentum | kg·m²/s |
Linear momentum describes the motion of an object through space, while angular momentum describes rotational motion.
Frequently Asked Questions
What is the SI unit of angular momentum?
The SI unit of angular momentum is kg·m²/s (kilogram meter squared per second).
Can angular momentum be measured in J·s?
Yes. J·s (joule-second) is equivalent to kg·m²/s.
What is the symbol for angular momentum?
Angular momentum is usually represented by the symbol L.
What is the dimensional formula of angular momentum?
The dimensional formula is [M L² T⁻¹].
What is the formula for angular momentum?
For a rotating rigid body, the formula is L = Iω, where I is the moment of inertia and ω is the angular velocity.