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Collisions and the Center of Mass

Collisions and the Center of Mass: Momentum and its conservation during collisions is introduced. Kinetic energy can decrease or increase during collisions. When kinetic energy is conserved, we call it an elastic collision. The momentum vector, internal forces, external forces and the conservation of momentum are discussed. Professor Lewin does some air track experiments where the released energy is from a compressed spring; kinetic energy increases but momentum is conserved. The definition of the center of mass is described. The center of mass behaves as if all the matter were together at that point.