Section 3: Conservation of Energy

Where Does the Energy Go? Introduction Energy is not lost—it changes form Where Does the Energy Go? Friction—force that opposes motion Example: Roller coaster converts energy Uses some PE as… Kinetic energy to move down tracks Thermal energy created by friction

Energy is conserved within a closed system Closed system—well-defined group of objects that transfers energy between on another Example: Roller coaster system includes: track, cars, air ME (PE + KE) converted to thermal energy, kinetic energy, and sound energy Add together KE, thermal energy, sound energy at the end and it equals the same amount as the original amount of PE Energy is conserved

Law of Conservation of Energy Energy all conserved Law of conservation of energy—energy can neither be created nor destroyed Total amount of energy is always the same Energy changes form but always adds up to the same as the initial PE Example: Light Bulb System: outlet, wire, bulb Electrical energy entering the light = total amt. of light + thermal energy Energy is conserved

No Conversion Without Thermal Energy Within a conversion always converts to thermal energy Thermal energy due to friction not useful energy Perpetual Motion? No way! Perpetual Motion Machine—machine that runs forever without any additional energy Does not exist only way is to have continual energy source

Section 4: Energy Resources Energy resources—natural resource that can be converted by humans into other forms of energy Sun—responsible for the most resources Nonrenewable Resources Cannot be replaced after they are used Fossil fuels most important type

Fossil Fuels Energy resources formed from buried remains of plants and animals Example: coal, petroleum, natural gas Sun’s energy converted by plants—energy used by animals that eat those plants Coal—burned to produce steam run electrical energy Petroleum—used for gas, kerosene, wax, synthetic fibers Natural gas—used for heating; cleanest burning fuel

Electrical Energy from Fossil Fuels Generate electrical energy by burning fossil fuels Kinetic energy is converted to electrical energy by electric generator Nuclear Energy Nuclear energy generated from radioactive element (uranium) Nuclear fission—uranium splits into two nuclei—considered nonrenewable resource

Renewable Resources Can be used and are replaced by nature Solar Water Wind Geothermal Biomass—organic material that is burned to release energy

The two sides to energy resources Depending on the location, purpose, amount of energy needed—some energy resources are better than others