ASTR 20 Lecture Notes - Lecture 20: Angular Momentum, Thermal Energy, Conservation Law
Document Summary
Interacting objects exchange momentum through equal and opposite forces. The total momentum of interacting objects cannot change unless an external force is acting on them. The angular momentum of an object cannot change unless an external twisting force (torque) is acting on it. Earth experiences no twisting force as it orbits the sun, so its rotation and orbit will continue. Angular momentum conservation also explains why objects rotate faster as they shrink in radius. Distance (r) is greater so velocity (v) is smaller. Distance (r) is smaller so velocity (v) is greater. Energy can change type but cannot be destroyed. The collective kinetic energy of many particles. Thermal energy is related to temperature but it is not the same. Temperature is the average kinetic energy of the particles in a substance. Thermal energy is a measure of the total kinetic energy of all the particles in a substance.
