1. Physical Science Ch. 4

2. Section 1

3. EnergyEnergy –is the ability to cause change Two types of energyTwo types of energy –Potential Energy –Kinetic Energy

4. Kinetic energyKinetic energy –Energy in the form of motion –The amount of kinetic energy an object has depends on its mass and its velocity K.E. = ½ (mass)*(velocity) 2K.E. = ½ (mass)*(velocity) 2 JouleJoule –The SI unit used to measure energy –Equivalent to Newton-meter

5. Potential energyPotential energy –Energy stored –Energy of position Elastic potential energyElastic potential energy –Energy stored by things that stretch or compress Chemical potential energyChemical potential energy –Energy stored in chemical bonds between atoms

6. Gravitational potential energyGravitational potential energy –Stored energy (by things above earth) –The amount of GPE an object has depends on its mass, the acceleration due to gravity, and its height above ground. –mass * acceleration due to gravity * height off ground PE = m * g * hPE = m * g * h –Measured in Joules (Newton- meter) *Remember g = 9.8 m/s 2*Remember g = 9.8 m/s 2

7. Section 2

8. Energy conversionsEnergy conversions –energy changing from one form to another –Fuels store energy in the form of chemical potential energy. Mechanical energyMechanical energy –the total amount of potential and kinetic energy in a system

9. Law of Conservation of EnergyLaw of Conservation of Energy –Energy may change from one form to another, but the total amount of energy never changes –Energy can neither be created nor destroyed, it just changes forms

10. Law of Conservation of Energy ExampleExample –As a swing moves back and forth, its energy continually converts from kinetic to potential & back –If the energy of the swing decreases, then the energy of some other object must increase by an equal amount –Friction converts some of the mechanical energy into thermal energy.

11. Converting mass into energyConverting mass into energy –You must think of mass as energy when discussing nuclear reactions –The total amount of mass and energy is conserved Nuclear fusionNuclear fusion –Two nuclei are fused together –Takes place in the sun Nuclear fissionNuclear fission –Two nuclei are broken apart.

12. Conservation of energy in your bodyConservation of energy in your body –chemical potential energy from food that is stored in your body is used to fuel the processes that keep you alive CalorieCalorie –used to measure how much energy you get from various foods –One Calorie is equivalent to about 4,180 Joules