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Energy 2

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Energy 2

1. 1. ENERGY By
2. 2. Work <ul><li>Formula: </li></ul><ul><li>Work= Force * Distance </li></ul><ul><li>W=FD </li></ul>
3. 3. Example of Work <ul><li>Lifting a load against Earth’s gravitational pull </li></ul><ul><li>For example, this man is attempting to lift a box off of the ground against the pull of gravity. </li></ul>
4. 4. Continued <ul><li>The heavier the load and the higher we lift the object, the more work we do. </li></ul><ul><li>Superman here is doing quite the amount of work because he is lifting a very heavy mass, while at the same time lifting it high into the air. </li></ul>
5. 5. Example 2 <ul><li>Weight lifting </li></ul><ul><li>Work is done when lifting a barbell. The higher the mass, and the higher the barbell is lifted, the more work is done. </li></ul>
6. 6. Hold up <ul><li>Contrary to the past two slides, though the amount of work done depends on the displacement and the mass of the object, if a object is standing still, no work is being done </li></ul>
7. 7. Explanation <ul><li>Ok lets go back to superman, when he lifted the car above his head, he did a tremendous amount of work. However, now that the car is being held idly above his head, he is doing zero work. </li></ul>
8. 8. Categories <ul><li>Work is generally separated into two different categories </li></ul>
9. 9. 1 <ul><li>Work done against another force </li></ul><ul><li>For example: an archer stretching his bow and arrow </li></ul>
10. 10. 2 <ul><li>Work done to change the speed of an object </li></ul><ul><li>Example: bringing a car in motion to a stop. </li></ul>
11. 11. Unit of Measurement <ul><li>Joule </li></ul><ul><li>1 Newton exerted over 1 meter </li></ul><ul><li>That guy is James Joule, the guy the unit is named after </li></ul>
12. 12. Sample Question <ul><li>How much work is done on a 100N boulder that you carry horizontally across a 10m room? </li></ul><ul><li>CLICK FOR ANSWER </li></ul>
13. 13. Power <ul><li>Formula: </li></ul><ul><ul><ul><li>Power = Work divided by Time </li></ul></ul></ul><ul><ul><ul><li>P=W/t </li></ul></ul></ul>
14. 14. Power <ul><li>Power is the measure of how long it takes you to do work. </li></ul><ul><li>Example: How long it takes to run up a flight of stairs </li></ul>
15. 15. Unit of Measurement <ul><li>Watts </li></ul><ul><li>1 Joule in 1 sec </li></ul><ul><li>That’s James Watt </li></ul>
16. 16. Sample Question <ul><li>What power is expanded if you lift a 100N boulder a distance of 1 m in a time of 1 s </li></ul><ul><li>CLICK FOR ANSWER </li></ul>
17. 17. Types of Energy
18. 18. Mechanical <ul><li>Mechanical energy is the energy due to the position of something, or the movement of something </li></ul><ul><li>There are two types of mechanical energy </li></ul>
19. 19. Potential Energy <ul><li>Potential energy is stored energy in an object. </li></ul><ul><li>Formula: PE=mgh </li></ul><ul><li>Example: in a stretched rubber-band, energy is stored in the rubber band then used when released. </li></ul>
20. 20. Kinetic Energy <ul><li>Kinetic energy is energy used in motion. </li></ul><ul><li>Formula: 1/2(m)(v)(v) </li></ul><ul><li>Example: A runner is expanding kinetic energy. </li></ul>
21. 21. Sample Question <ul><li>When the brakes of a motorcycle traveling at 60km/h become locked, how much further than the motorcycle skid than if it travels at 20km/h? </li></ul><ul><li>CLICK FOR ANSWER </li></ul>
22. 22. Law of Conservation of Energy <ul><li>Energy cannot be created or destroyed. It can be transformed from one form into another, but the total amount of energy never changes </li></ul>
23. 23. Efficiency <ul><li>Useful work output </li></ul><ul><li>Total work input </li></ul><ul><li>That fraction will always be less than one. </li></ul>
24. 24. Answer <ul><li>Power= 100J/1s=100W </li></ul><ul><li>100 Watts </li></ul><ul><li>CLICK TO GO BACK TO PREVIOUS SLIDE </li></ul>
25. 25. Answer 2 <ul><li>You do not work on the boulder moved horizontally, because you apply no force (except for the tiny bit to start and stop it) in its direction of motion. </li></ul><ul><li>CLICK TO GO BACK </li></ul>
26. 26. Answer 3 <ul><li>Nine times farther; the motorcycle has nine times as much kinetic energy when it travels three times as fast. </li></ul><ul><li>CLICK TO GO BACK </li></ul>