A law in physics is an empirical statement describing how nature always behaves. The evidence used to support the validity of the law must be incontrovertible. And any event or discovery that can show that a law as stated is less than accurate can cause the law to be rewritten, modified, or discarded and supplanted by a new law. Two fundamental laws will be presented in this unit, the Law of Conservation of Energy and the Law of Conservation of Momentum. The word conservation in the context of this chapter means that we can account for the energy or momentum in any system before, during, and after any event. Conservation in the context of physics does not usually mean saving or not wasting.

Conservation of energy


  Conservation of Momentum

  Conservation of Mass & Mass-Energy