Work done
A force does work when it moves something: force times the distance moved in the direction of the force. Only the component along the motion counts.
≈ 30 minKinetic and potential energy
Kinetic energy is the energy of motion, ; potential energy is the energy of height, . With no friction or air resistance, one simply turns into the other and the total never changes.
≈ 30 minThe work–energy principle
Energy is never lost, only moved around. Work done by a driving force goes into kinetic energy, potential energy, and the work done against resistances. Balance the books and the unknown drops out.
≈ 40 minPower
Power is how fast work is done: joules per second, or watts. For a vehicle, , so the same engine pushes hard at low speed and gently at high speed, which is why every car has a top speed.
≈ 35 min