Table of Contents 2 13 20 21 29
Table of Contents 2 13 20 21 29 Concept Development 12 -1 Concept Development 13 -2 Concept Development 13 -3 Concept Development 14 -1 1
Concept Development 12 -1 Created for CVCA Physics By Dick Heckathorn 17 February 2 K + 5 2
1. Inverse Square Law 4 1/4 9 1/9 16 1/16 3 CD 12 -1 p 49
Inverse Square Law At 4 d 3 d 2 d 5 d apple weighs 1/9 1/25 1/4 1/16 NN 4
Demo Distorted Room 5
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Distorted Room or. . . 7
2. Inverse Square Law 25 m 2 5 m from the source? 100 m 2 CD 12 -1 p 49 8
3. Inverse Square Law Hold one hand twice as far away as the other hand. You see…. . 9 CD 12 -1 p 49
Demo Sun-Earth-Moon 11
Sun Earth Moon Allignment 12
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 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. 13 CD 13 -1 p 51
The weight of the apple is a different story. It may weight exactly 1 N in San Francisco and slightly less in milehigh 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 weight the quantity that may change mass and is its mass weight. 14 CD 13 -1 p 51
the force due That’s because weight, is mass 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 weight, of mass an object we are usually speaking of the gravitational force that attracts it to the earth. 15 CD 13 -1 p 51
2. Force and Weight The answers are: …weigh 500 N …force of 500 N, …weights 500 N! 16 CD 13 -1 p 51
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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). 18 CD 13 -1 p 52
5. a Fill in the weights of the object on the planet’s shrinking surface. 4 1 100 b. Object is still collapsed and a ladder it erected ‘R’ distance long 19 CD 13 -1 p 51
Concept Development 13 -2 1. Fnew = 4 Fold 2. Fnew = 4 Fold CD 13 -1 p 53 3. Fnew = 16 Fold 4. Fnew = Fold no change 5. Fnew = 2/9 Fold 6. Fnew = Fold no change CD 13 -1 p 54 20
Concept Development 13 -3 a. force vector on B. d. b. c. Why? Is thisthe Which force has the more, greater less, acceleration? the sameofas 1. Draw Consider two equal-mass blobs A? water, A and B, initially at rest in the moon’s gravitational field. The vector shows the gravitational force of the moon on A. 21 CD 13 -1 p 55
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. 22 CD 13 -1 p 55
Concept Development 13 -3 f. If A and B were connected by a rubber band, with time the rubber band would stretch. 23 CD 13 -1 p 55
Concept Development 13 -3 g. This stretching is due to the difference in the moon’s gravitational pulls. 24 CD 13 -1 p 55
Concept Development 13 -3 their accelerations will consist h. Then The two blobs will eventually crash of changes in direction into the moon. To orbit around only. the moon instead of crashing into it, the blobs should move tangentially. 25 CD 13 -1 p 55
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. 26 CD 13 -1 p 55
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 27 CD 13 -1 p 55
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 28 CD 13 -1 p 55
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 29 CD 13 -1 p 56
d-R d d+R d = 3. 8 x 108 m R = 6. 38 x 106 m Mm = 7. 34 x 1022 kg mon w = 1 x 106 kg Fd+R = 3. 28 x 101 = 32. 8 N Fd-R = 3. 51 x 101 = 35. 1 N 30 CD 13 -1 p 56
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 p 56 31
Satellite Motion 14 -1 km/sec < = 82 km/sec VVV = << 0. 05 km/sec 34 CD 13 -1 p 57
2. Satellite Motion v v F F v CD 13 -1 p 57 v 35
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. speed? A b. velocity? A c. momentum? A d. kinetic energy? A e. grav pot energy? C f. total energy? same-same CD 13 -1 p 58 36
That’s all folks! 37
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