Unit 4: Linear Momentum

Unit 4 is linear momentum, p = mv, a vector. Impulse (FΔt, or area under a force-time graph) equals the change in momentum, which is why airbags and padding work: more time means less force. When no net external force acts on a system, total momentum is conserved in every collision. Kinetic energy is conserved only in elastic collisions; in perfectly inelastic collisions the objects stick together and the most kinetic energy is lost. Combine momentum and energy for multi-step problems like the ballistic pendulum, and treat 2D collisions one component at a time.