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Work

Work. “Quiz ” tomorrow. You lift a 3 N book 2 m. How much work did you do? 3 N x 2 m = 6 J. If 40 J of work is done on a 2 N object, how far did it go? 40 J/2 N= 20 m. You carry a 3 N book 5 m. How much work did you do? 0 J. You lift two 4 N books 2 m. How much work did you do?

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Work

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  1. Work “Quiz” tomorrow

  2. You lift a 3 N book 2 m. How much work did you do? • 3 N x 2 m = • 6 J

  3. If 40 J of work is done on a 2 N object, how far did it go? • 40 J/2 N= • 20 m

  4. You carry a 3 N book 5 m. How much work did you do? • 0 J

  5. You lift two 4 N books 2 m. How much work did you do? • (4N + 4N) x 2m = • 16 J

  6. A crew member uses 800 N to row an oar’s handle 0.5 m. How much work did the crew member do? • 800 N x 0.5 m = • 400 J

  7. You lift your 50 N cousin 1.5 m. How much work do you do? 50 N x 1.5 m = 75 J

  8. You went shopping and filled two bags. You need to carry both bags up the stairs. Would you do more work if you carried one bag at a time or both bags at the same time? • The work would be the same (one bag at a time would be more distance, since you would lift the bag up the stairs twice, though it would be ½ the N, and two bags would be ½ the distance, since you’d only be going upstairs once).

  9. A giraffe lifts his 3 N head 2 m. How much work did he do to reach the food on the top branch? • 3 N x 2 m = • 6 J

  10. A soccer player kicks a 1 N ball 8 m to the goal. How much work would the goalie have to do in order to stop the ball? • 1 N x -8 m = • -8 J • Negative because the goalie is working opposite the kicker.

  11. A student lifts three 3 N books 0.5 m. How much work did the student do? • (3 x 3 N) x 0.5 m = • 4.5 J

  12. Who did more work: a girl who lifts five 1 N boxes 1 m or another girl who carries a 7 N suitcase 3 m? • First girl: • (5 x 1 N) x 1 m= • 5 J • Second girl: • 7 N x 0 m (she is not carrying the suitcase in the direction of the work!) = • 0 J • The girl with the boxes

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