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  1. THIS PAGE WILL BE GONE IN 5 mins BE SURE TO HAVE YOUR ID VISIBLE AROUND YOUR NECK, NO NON-POLY ATTIRE! DRILL: power Date: Jan 30, 2012 How many Joules of work are used by a 100 w bulb in 2 minute? OBJECTIVE Define and solve word on potential energy. HOMEWORK Copy and answer no. 10 & 13 of page 292 Note: Quiz on power work & energy on Friday. Feb 3

  2. THINK ABOUT! WHAT IS ENERGY?

  3. Energy THE ABILITY TO DO WORK!

  4. MECHANICAL Car, plane, wagon THERMAL Heat from moving molecules Inside all matter; furnace ELECTROMAGNETIC Visible light, microwaves, radio waves CHEMICAL Batteries, matches, body cells ELECTRICAL Lightning, power lines NUCLEAR Nuclear power plants, atomic bomb, sun & stars TYPES OF ENERGY

  5. Mechanical Energy When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy.

  6. Kinetic Energy Potential Energy Elastic Potential Energy Gravitation Potential Energy Chemical Potential Energy How is MECHANICAL energy divided? MECHANICAL ENERGY

  7. POTENTIAL ENERGY!

  8. A Roller Coaster As it slows to a stop at the top of a hill, it has potential energy because of where it is. It has the potential to move because it is above the ground and has somewhere to go.

  9. Substances like wood, coal, oil, and gasoline have storedenergy because of their chemistry – they can burn Stored energy is potential energy

  10. What is Potential Energy? • Energy that is stored and waiting to be used later

  11. Potential Energy • Stored chemically in fuel, the nucleus of atom, and in foods. • Or stored because of the work done on it: • Stretching a rubber band. • Winding a watch. • Pulling back on a bow’s arrow. • Lifting a brick high in the air.

  12. Gravitational Potential Energy ENERGY THAT DEPEND ON HEIGHT

  13. Gravitational Potential Energy A waterfall, a suspension bridge, and a falling snowflake all have gravitational potential energy.

  14. Gravitational Potential Energy If you stand on a 3-meter diving board, you have 3 times the G.P.E, than you had on a 1-meter diving board.

  15. Gravitational Potential Energy “The bigger they are the harder they fall” is not just a saying. It’s true. Objects with more mass have greater G.P.E. The formula to find G.P.E. is GPE = Fg X h

  16. What is Gravitational Potential Energy? • Potential energy due to an object’s position • P.E. = mass x height x gravity Don’t look down, Rover! Good boy!

  17. Elastic Potential Energy • Energy that is stored due to being stretched or compressed is called elastic potential energy.

  18. What is Elastic Potential Energy? • Potential energy due compression or expansion of an elastic object. Notice the ball compressing and expanding

  19. What is Chemical Potential Energy? • Potential energy stored within the chemical bonds of an object

  20. Potential Energy Potential energy exists whenever an object which has mass has a position within a force field. The most everyday example of this is the position of objects in the earth's gravitational field. The potential energy of an object in this case is given by the relation: PE = mgh  PE = Energy (in Joules) m = mass (in kilograms) g = gravitational acceleration of the earth (9.8 m/sec2) h = height above earth's surface (in meters)

  21. QUESTION If A and B are both the same height, Do they have the same amount of Potential Energy?

  22. PRACTICE PROBLEM 1 A hallway display of energy is constructed in which several people pull on a rope that lifts a block 1 m. The display indicates that 1 Joule of work is done. What is the mass of the block?

  23. PRACTICE PROBLEM 2 Antwan raised a 12 N physics book from a table 75 cm above the floor to a shelf 2.15 m above the floor. What was the change in the PE of the system?

  24. CLASSWORK On a separate sheet of paper, DON’T COPY QUESTION/ PROBLEM Part 1. Answer in a complete sentence No. 4 [a-b], 6 & 9 of page 267 Part 2. Show work! – knowns & unknowns No. 44-48 of page 269

  25. WRAP-UP Copy and answer OR answer in a complete sentence What are the quantities that describes potential energy? REMINDERS! Only absences/ missed work with pink slips can be made up MISSING A DETENTION = 0 IN ALL OUTPUTS FOR THAT DAY [includes notebook] COACH CLASS Tues & Thurs, 3:15 – 4:00, RM 127 QUIZ ON work power & energy on FEB 3 Notebooks will be checked on FEB 3…