Internal Forces: Internal forces are forces exerted between objects within a system. In collisions, internal forces are responsible for changes in momentum and kinetic energy.
Net Work: Net work is the total amount of work done on or by an object when multiple forces act upon it. It takes into account both external and internal forces.
Conservation of Energy: The principle of conservation of energy states that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another. In other words, the total energy in a closed system remains constant over time.