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Get to Work!

Get to Work!. Ms. Moore 9/10/12. What is work?. What does “work” mean to you? Work is the transfer of energy when a force makes an object move. Work makes something MOVE. Doing Work. For work to be done, these conditions have to be satisfied: The applied force must make the object move.

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Get to Work!

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  1. Get to Work! Ms. Moore 9/10/12

  2. What is work? • What does “work” mean to you? • Work is the transfer of energy when a force makes an object move. • Work makes something MOVE

  3. Doing Work • For work to be done, these conditions have to be satisfied: • The applied force must make the object move. • Movement must be in the same direction as the applied force. • Examples: • A student picks up a stack of books. Would this be an example of work? Why or why not? • A student walks with the books. Is this an example of work? Why or why not?

  4. Relationship of Work and Energy When work is done, a transfer of energy always occurs. This is why you feel tired when you carry something up stairs. You have transferred energy. Muscles  box = increase in potential energy Explain how energy of the box changes as you walk up a flight of stairs.

  5. How do we calculate work? The amount of work done depends on the amount of force exerted and the distance which it is applied. When a force is exerted and an object moves in the direction of the force: work (J) = applied force (N) x distance (m) **Work is only calculated when the force is being applied.

  6. Practice A couch is pushed with a force of 75N and moves a distance of 5m across the floor. How much work is done in moving the couch? A lawn mower is pushed with a force of 80N. If 12,000J of work are done in mowing a lawn, what is the total distance the lawn mower was pushed? The brakes on a car do 240,000J of work in stopping the car. If the car travels a distance of 50m while the brakes are being applied, what is the force the brakes exert on the car?

  7. I have the Power • What is power? • Power is the amount of work done in one second or the rate at which work is done. • How can you calculate power? • Divide work by the amount of time it took to complete. Power (watts) = work (J)/time (s)

  8. Mini Lab • Page 129: Calculate your work and power • 5 volunteers to exercise, 5 to walk • Record your observations. • Height/Distance • Time • Return to class to calculate work and power. • Answer questions on page 129.

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