Lecture
This lecture introduces two new physical quantities: angular momentum and torque, and their close relationship known as the angular momentum theorem. Angular momentum is defined as the cross product of the position vector and the momentum of a material point, while torque is defined as the cross product of the position vector and a force. The angular momentum theorem states that the time derivative of angular momentum equals the torque. The demonstration of this theorem involves applying the definitions of angular momentum and torque, showing that the derivative of their product yields the torque. The lecture emphasizes the dependence of these quantities on the choice of reference point.