1. Ch.9, Sec.3 – Conservation of Energy
Where Does the Energy Go?
friction: a force that opposes motion between two surfaces that are in contact
on a roller coaster, not all potential energy is converted into kinetic energy because of friction!
kinetic energy can be converted into thermal energy instead of going back to potential
Energy Is Conserved Within a Closed System
a closed system is a group of objects that transfer energy only to each other
energy is always conserved and never lost!

2. Ch.9, Sec.3 – Conservation of Energy
law of conservation of energy: this law states that energy cannot be created or destroyed but can change from one form to another
the total amount of energy in a closed system is always the same
energy is conserved in all cases & no exception has been found!
No Conversion Without Thermal Energy
thermal energy due to friction is NOT useful (it cannot be used for work)
example: car (wasted thermal energy leaves the radiator & the exhaust)

3. Ch.9, Sec.3 – Conservation of Energy
perpetual motion is NOT possible because a constant energy supply is needed
energy efficiency is a comparison of the amount of energy before a comparison with the amount of useful energy after a conversion