|What is Friction?
||A force that opposes motion between two surfaces that are in contact.
|What is the Law of Conservation of Energy?
||The law that states that energy cannot be created or destroyed but can be changed from one form to another.
|Why is the law of conservation of energy considered a scientific law?
||Because no exception to it has ever been observed
|What is a closed system?
||A group of objects that transfer only to each other.
|Why is "perpetual motion" impossible?
||Because energy conversions always result in the production of waste thermal energy
|What is energy efficiency?
||the comparison of the amount of energy before a conversion with the amount of useful energy after a conversion.