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P H Y S I C S Introduction to Work, Power & Kinetic Energy

P H Y S I C S Introduction to Work, Power & Kinetic Energy. What is Work?. What do you think of when you think of work?. Work. Work is done when a force acts parallel to the direction of the displacement. Force. Displacement. Force. Displacement. Work.

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P H Y S I C S Introduction to Work, Power & Kinetic Energy

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  1. P H Y S I C S Introduction to Work, Power & Kinetic Energy

  2. What is Work? • What do you think of when you think of work?

  3. Work Work is done when a force acts parallel to the direction of the displacement Force Displacement Force Displacement

  4. Work Work is done when a force acts parallel to the direction of the displacement Friction Force Displacement Air Resistance Force Displacement

  5. Work or Not? • Man holds out heavy concrete block at arm’s length for 10 minutes • Student pushes car down street • Women holds up a large box over-head while walking down the hall way • Child pushes a cart along the side walk NOT WORK WORK NOT WORK WORK

  6. What is kinetic energy? • What do you think of when you think of kinetic energy?

  7. Kinetic Energy • Any moving object has kinetic energy • Amount depends on 1) velocity 2) mass

  8. Kinetic Energy Equation KE  kinetic energy (J) m  mass (kg) v  velocity (m/s) Note:

  9. Kinetic Energy

  10. Work-Energy Theorem • Work done on an object is equal to its change in kinetic energy W = ∆KE W  work (J) ∆KE  change in kinetic energy (J) Note:

  11. Work-Energy Theorem • +W increases KE WORK

  12. Formula for Work • W = f * d • W  Work (J) • f  Force (N) • d  Displacement (m)

  13. What is power? • What makes something powerful?

  14. Power • The rate at which work is done

  15. Work vs. Power • Power accounts for “how fast” work is done A B

  16. Power Equation Unit: • P  power (W) • W  work (J) • t  time (s)

  17. Power Equation • Another variation derived from : • P  power (W) • F  force (N) • v  velocity (m/s)

  18. Household Appliances • 60W light bulb - 60W • Toaster : 800-1500W • Microwave : 600-1500W • Dishwasher : 1200-1500W • Washing Machine : 500W • Vacuum Cleaner : 200-700W • Clothes dryer : 4000W • Ceiling Fan : 10-50W • Hair Blow dryer : 1000W • Laptop Computer : 20-50W • Desktop Computer : 80-150W • Cell Phone Charger: 3-5W • iPod/iPad Charger: 10W

  19. Time to explore Power • What do we need to know to calculate power? • What is your force? • So if 1lb=2.2kg how much mass do you have? • How can we calculate velocity?

  20. On a sheet of paper • Calculate your Fg. • Now let’s go to the stairs and see who can generate the most power. • When we get back calculate your power. This paper is your exit slip. You can’t leave until it’s done.

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