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What is work?

What is work?. The Meaning of work, calculating work & power. work. Work is done on an object when the object moves in the same direction in which the force is exerted . Ex: Push a child on a swing Pull your books out of your backpack Lift a book. Work questions. Pick up your backpack?

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What is work?

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  1. What is work? The Meaning of work, calculating work & power

  2. work • Work is done on an object when the object moves in the same direction in which the force is exerted. • Ex: • Push a child on a swing • Pull your books out of your backpack • Lift a book

  3. Work questions • Pick up your backpack? • Carried your backpack at school? • Carry books to your desk? • Pull open a door? • Push your friend in the hall? • Lift weights above your head?

  4. Work done? • Force is not in the direction motion. • No work is done

  5. Work done? • Force is in the samedirection of motion • Work is done!

  6. Horizontal part of the force does work.

  7. Calculating work • Work = Force x Distance • Lifting an object: the upward force must be at least equal to the object’sweight. • When you lift a plant, you do work. If you exert a force of 50 N and lift the plant 0.5 meters, what is the work you do? • Work = 50 N x 0.5 m • 25 Nm (Newton meters)

  8. Demo: Pinwheel • Is work always the same? • Dryer on high setting • Observe pinwheel motion • Dryer on low setting. • Observe pinwheel motion. • Explain why work is done on the pinwheel. • How are the two situations different? • Is the amount of work greater for the high or low setting? • Why? • Where would you infer the best locations for windmills to be placed to produce electricity?

  9. power • What are some things you would describe as powerful? • What characteristics do all these things share? • Power: the rate at which work is done.

  10. rate? • How much of something happens in a certain time period. • Power = work/time • Unit of power = J/s

  11. Power Questions • More power to run up the stairs with your backpack or walk ? • Which has more power? Raking the leaves or using a blower? • Which does more work? Raking leaves or using the blower?

  12. Power • Object that has more power does more work in the same time. • or • Same amount of work in less time.

  13. Doing work?

  14. Question Answer Asking Questions Work is done when an object moves in the same direction in which the force is exerted. What is work? How can you calculate work? Work = Force X Distance Power is the rate at which work is done. What is power?

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