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Table of Contents

Table of Contents. Concept Development 12-1 Concept Development 13-1 Concept Development 13-2 Concept Development 13-3 29 Concept Development 14-1. Concept Development 12-1. Created for CVCA Physics By Dick Heckathorn 17 February 2K + 5. 1. Inverse Square Law. 4. 9. 16. 1/4. 1/16.

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Table of Contents

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  1. Table of Contents • Concept Development 12-1 • Concept Development 13-1 • Concept Development 13-2 • Concept Development 13-3 29 Concept Development 14-1

  2. Concept Development 12-1 Created for CVCA Physics By Dick Heckathorn 17 February 2K + 5

  3. 1. Inverse Square Law 4 9 16 1/4 1/16 1/9 CD 12-1 p49

  4. Inverse Square Law At 4d apple weighs At 3d apple weighs At 2d apple weighs At 5d apple weighs 1/9 N 1/25 N 1/4 N 1/16 N

  5. Demo Distorted Room

  6. Distorted Room or . . .

  7. 2. Inverse Square Law 25 m2 5 m from the source? 100 m2 10 m from the source? CD 12-1 p49

  8. 3. Inverse Square Law Hold one hand twice as far away as the other hand. You see….. CD 12-1 p49

  9. Demo Sun-Earth-Moon

  10. Sun Earth Moon Allignment

  11. Concept Development 13-1 1. An apple that has a mass of 0.1 kg has the same mass wherever it is. The amount of matter that makes up the apple does not depend depends on upon the location of the apple. It has the same resistance to acceleration wherever it is—its inertia everywhere is the same. different. CD 13-1 p51

  12. The weight of the apple is a different story. It may weight exactly 1 N in San Francisco and slightly less in mile-high Denver. On the surface of the moon the apple would weigh 1/6 N, and far out in space it may have almost no weight at all. The quantity that doesn’t change with location is and the quantity that may change is its weight mass weight. mass CD 13-1 p51

  13. is the force due to gravity on a body, and this force varies with distance. So weight is the force of gravity between two bodies, usually some small object in contact with the earth. When we refer to the That’s because weight, mass weight, mass of an object we are usually speaking of the gravitational force that attracts it to the earth. CD 13-1 p51

  14. 2. Force and Weight The answers are: …weigh 500 N. …weigh 500 N …force of 500 N, …force of 500 N, …weights 500 N! CD 13-1 p51

  15. CD 13-1 p52

  16. 4.a Fill in the gravitational force on the object at R/2 and R = 0. 1/2 0 The motion would be: to and fro (in simple harmonic motion). CD 13-1 p52

  17. 5. a Fill in the weights of the object on the planet’s shrinking surface. 1 4 100 b. Object is still collapsed and a ladder it erected ‘R’ distance long CD 13-1 p51

  18. Concept Development 13-2 1. Fnew = 4 Fold 2. Fnew = 4 Fold CD 13-1 p53 3. Fnew = 16 Fold 4. Fnew = Fold no change 5. Fnew = 2/9 Fold 6. Fnew = Fold no change CD 13-1 p54

  19. Concept Development 13-3 a. Draw the force vector on B. b. Is this force more, less, the same as A? d. Which has the greater acceleration? c. Why? 1. Consider two equal-mass blobs of water, A and B, initially at rest in the moon’s gravitational field. The vector shows the gravitational force of the moon on A. CD 13-1 p55

  20. Concept Development 13-3 e. Because of different accelerations, with time A gets further ahead of B and the distance between A and B increases. CD 13-1 p55

  21. Concept Development 13-3 f. If A and B were connected by a rubber band, with time the the rubber band would stretch. CD 13-1 p55

  22. Concept Development 13-3 difference stretching is due to the g. This in the moon’s gravitational pulls. CD 13-1 p55

  23. Concept Development 13-3 Then their accelerations will consist of changes in h. The two blobs will eventually crash into the moon. To orbit around the moon instead of crashing into it, the blobs should move direction only. tangentially. CD 13-1 p55

  24. 2. Now consider the same two blobs located on opposite sides of the earth. a. Because of differences in the moon’s pull on the blobs, they tend to spread away from each other. approach each other b. This spreading produces ocean tides. CD 13-1 p55

  25. c. If earth and moon would be closer, gravitational forces between them would be more, the same, less and the difference in gravitational forces on the near and far parts of the ocean would be more, the same, less CD 13-1 p55

  26. d. Because the moon’s orbit is slightly elliptical, earth and moon are closer in winter months than in summer. On a world average, then, ocean tides are greater in December, June no difference CD 13-1 p55

  27. d-R d d+R a. Which of the two forces: moon on left mass (m) or moon on right mass (m) is stronger and why? Fd-R CD 13-1 p56

  28. d-R d d+R Mm = 7.34 x 1022 kg d = 3.8 x 108 m monw = 1 x 106 kg R = 6.38 x 106 m Fd+R = 3.28 x 101 = 32.8 N Fd-R = 3.51 x 101 = 35.1 N CD 13-1 p56

  29. What would happen to the orbit of the moon if the earth suddenly disappeared? • Find force of sun on moon • 4.366 x 1020 N • Find force of earth on moon • 2.027 x 1020 N CD 13-1 p56

  30. Satellite Motion 14-1 V << 2 km/sec V < 8 km/sec V = 8 km/sec V = 0.05 km/sec CD 13-1 p57

  31. 2. Satellite Motion v v F F F F v v CD 13-1 p57

  32. Consider the various positions of the satellite as it orbits the planet as shown. With respect to the planet, in which position does the satellite have the maximum: A a. speed? b. velocity? A c. momentum? A A d. kinetic energy? C e. grav pot energy? f. total energy? same-same CD 13-1 p58

  33. That’s all folks!

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