Work, Energy & Power — A/L Physics

Work (W) The product of force and displacement in the direction of the force. Work is done only when a force causes a displacement. If the force is perpendicular to displacement, no work is done. For example, carrying a bag horizontally — the vertical force of your hand does no work on the bag (displacement is horizontal). Work is a scalar quantity, measured in joules (J).

Kinetic Energy (K) The energy an object possesses due to its motion. A moving object can do work when it slows down. Kinetic energy depends on mass and the square of speed: doubling speed quadruples kinetic energy. A car at 80 km/h has four times the kinetic energy of the same car at 40 km/h — this explains why braking distances increase dramatically with speed.