PHYSICS
Rotating objects
Below are the properties and relations to rotating objects:
Velocity:
r
v
w
m
Angular momentum
The angular momentum L of an object with mass m is defined as the cross-product between its position vector r and its linear momentum vector p. It's measured relative to a chosen point.
By derivating this equation, we get to the definition of torque below. This is very important, as it states that if there's a torque on the object, then its angular momentum is changing in time. If there's no torque on the object, its angular momentum will be conserved.
In the special, and most used case, where an object is spinning around its center of mass, the chosen reference point doesn't matter. We call that its "spin angular momentum". It's an intrinsic property of an object given by the product between its moment of inertia I and its angular velocity w:
