A measure of the "amount of rotational motion" of a body; conserved when no external torque acts.
Symbols
L
angular momentum
[kg·m²/s]
I
moment of inertia
[kg·m²]
ω
angular velocity
[rad/s]
Where it comes from
The rotational counterpart of momentum. It is conserved when no external torque acts — that is why a skater who pulls their arms in (smaller I) spins faster (larger ω).
When to use it
Rotational motion, conservation of angular momentum.
Example
A rigid body with I=2 kg·m² rotates at ω=3 rad/s. Calculate the angular momentum.