Lecture
This lecture covers the general method for solving dynamics problems, including drawing a diagram, identifying external forces, applying Newton's law, choosing a reference frame, and solving scalar equations. It also discusses the concept of momentum and the third law of Newton, emphasizing that the forces between two parts of an object are equal in magnitude and opposite in direction. Examples of collisions between objects on a horizontal rail are used to illustrate the conservation of momentum. The lecture concludes by highlighting that the internal forces during a collision do not affect the conservation of momentum.