1. Physics Review Day 2

2. Energy Energy is conserved in a system, it can not be created or destroyed Energy is simply defined as Work There are two types: –Potential energy –Kinetic Energy Units: Joules, J

3. Kinetic Energy Energy in motion A increase in velocity causes a great proportional increase in kinetic energy Kinetic Energy = ½(mass x velocity 2 ) KE = ½ mv 2 Units: Joules, J

4. Potential Energy Energy Stored by an object Most important type is Gravitational Potential Energy GPE = mass x acceleration of gravity x height GPE = mgh Units: Joules, J

5. Work and Power

6. Work Work is the force applied to something over a distance Work = Force x Distance W = F x d Units: Joule, J

7. Power Power is work done over time Power = Work/ time P= W/t Units: Watts, W

8. Machines A device that makes work easier

9. Simple Machines Work is done with only one movement 6 basic machines –Lever –Inclined plane –Wedge –Screw –Pulley –Wheel

10. Compound Machines Two or more simple machines are used together

11. Measuring a Machine’s Efficiency For real machines, some of the energy put in is always lost as heat produced by friction; therefore, work output is less then work input Efficiency = (Work output / work input) x 100

12. Heat Transfer Conduction, Convection, and Radiation

13. Conduction Transfer of thermal energy due to direct contact with a solid

14. Convection Transfer of thermal energy through liquids and gases

15. Radiation Transfer of thermal energy through electromagnetic waves

16. Electric Circuits Closed, conducting path that electric charges follow

17. Circuit Units Voltage –The “push” that causes the charge to move –Measured in volts, V Current –Flow of the charge –Measured in amperes, A Resistance –A material’s tendency to oppose an electric flow –Measured in Ohms, Ω

18. Ohm’s Law Relates electric current, voltage difference, and resistance Current = Voltage/ Resistance Voltage = Current x Resistance I = V/R or V = IR

19. Series Circuit Provides only one path for the current to follow (contains only one loop) To solve for resistance: –R total = R 1 + R 2 + R 3 …

20. Parallel Circuits Current follows more than one path (contains more than 1 loop) This is used in houses R total = 1/R 1 + 1/R 2 …