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Warm-Up: December 5, 2011

Warm-Up: December 5, 2011. A 2.3 kg rock is thrown at a speed of 3.1 m/s into a stationary ball of clay. The rock gets stuck in the clay and they move together at a speed of 1.9 m/s. What is the mass of the clay?. Calculator Quiz Answers. Momentum and Impulse Worksheet . Momentum Assignments.

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Warm-Up: December 5, 2011

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  1. Warm-Up: December 5, 2011 • A 2.3 kg rock is thrown at a speed of 3.1 m/s into a stationary ball of clay. The rock gets stuck in the clay and they move together at a speed of 1.9 m/s. What is the mass of the clay?

  2. Calculator Quiz Answers

  3. Momentum and Impulse Worksheet

  4. Momentum Assignments • Conservation of Momentum WS due tomorrow • Homework due Wednesday: • Read Chapter 9 • Page 235 #7-9 • Page 250 #32-34, 38, 40, 57, 73, 80

  5. Questions about Momentum?

  6. Work and Power Section 10.1

  7. Work • Work is done when a force acting on an object causes it to move in the same direction of the force. • Work is equal to the product of force and distance • Work is represented by a capital “W” • Work has units Joules (J)

  8. Example 1 • A rope is pulling a box across the floor. If the tension of the rope is 125 N and the box moves 4.00 m, how much work was done?

  9. You-Try #1 • A man pushes his car 10.0 m down his driveway, pushing with a force of 250 N. How much work did the man do?

  10. Example 2 • A weightlifter lifts a barbell 0.70 m at a constant speed by exerting 140 J. What is the weight of the barbell?

  11. You-Try #2 • A woman pulls a refrigerator 0.50 m while exerting 250 J. With what force did she pull?

  12. Example 3 • How far can you push a box with a force of 75 N without exceeding 100.0 J?

  13. You-Try #3 • A mother goes for a walk while pushing a baby stroller with a force of 5.0 N. If she does 275 J of work on the stroller, how far did she walk?

  14. Warm-Up: December 6, 2011 • A child pulls a blanket 2.2 m while exerting 11 J. With what force did the child pull?

  15. Homework Questions?

  16. Calculator Quiz Answers

  17. Power • Power is the rate at which work is being done. • Power is represented by a capital “P” • “Work overtime to get more power.” • Power is measured in Watts (W)

  18. Example 4 • A rope is pulling a box across the floor. The tension of the rope is 125 N and the box moves 4.00 m. If it takes 20.0 s to move the box, how much power is used?

  19. You-Try #4 • A man pushes his car 10.0 m down his driveway, pushing with a force of 250 N. If the man takes 50.0 s to move his car, how much power did it take to move the car?

  20. Example 5 • A weightlifter lifts a barbell 0.70 m at a constant speed by exerting 140 J. If it takes 210 W to move the barbell, how many seconds did it take?

  21. You-Try #5 • A woman pulls a refrigerator 0.50 m using 300 W while exerting 250 J. How many seconds did it take to move the refrigerator?

  22. Example 6 • How much work is produced by a power of 125 W in exactly 30 seconds?

  23. You-Try #6 • If a runner uses 750 W for 15 s, how much work does she do?

  24. Example 7 • A box is pushed 14.9 m at a constant speed of 1.8 m/s. The box has a mass of 21 kg and the coefficient of kinetic friction between the box and the floor is 0.45. Calculate: • Force of gravity (weight) of the box • Normal force • Friction force • Push force • Work • The time it takes to move the box • Power

  25. Warm-Up: December 7, 2011 • A rope is pulling a box across the floor. The tension of the rope is 75.0 N and the box moves 3.00 m. If it takes 15.0 s to move the box, how much power is used?

  26. You-Try #7 • A box is pushed 7.9 m at a constant speed of 3.3 m/s. The box has a mass of 12 kg and the coefficient of kinetic friction between the box and the floor is 0.45. Calculate: • Force of gravity (weight) of the box • Normal force • Friction force • Push force • Work • The time it takes to move the box • Power

  27. Conservation of Momentum worksheet

  28. Assignments • Work and Power worksheet • For #6, air resistance is negligible. • Read Chapter 10 • Page 278 #52-57, 59

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