1. Table of Contents Concept Development 12-1 Concept Development 13-1

2. Created for CVCA Physics By Dick Heckathorn 17 February 2K + 5
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
1/9
1/16
CD 12-1 p49

4. Inverse Square Law At 3d apple weighs At 5d apple weighs

5. Demo Distorted Room

7. Distorted Room or . . .

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

9. 3. Inverse Square Law
Hold one hand twice as far away as the other hand. You see…..
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10. 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 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

13. and the quantity that may change is its weight mass weight.
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
mass
and the quantity that may change is its
weight
mass
weight.
CD 13-1 p51

14. 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

15. 2. Force and Weight The answers are: …weigh 500 N. …weigh 500 N
…force of 500 N,
…force of 500 N,
…weights 500 N!
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16. CD 13-1 p52

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

18. b. Object is still collapsed and a ladder it erected ‘R’ distance long
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
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19. Concept Development 13-2 1. Fnew = 4 Fold 2. Fnew = 4 Fold
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3. Fnew = 16 Fold
4. Fnew = Fold no change
5. Fnew = 2/9 Fold
6. Fnew = Fold no change
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20. Concept Development 13-3 b. Is this force more, less, the same as A?
d. Which has the greater acceleration?
a. Draw the force vector on B.
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.
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21. 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.
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22. Concept Development 13-3
f. If A and B were connected by a rubber band, with time the the rubber band would
stretch.
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23. Concept Development 13-3 g. This stretching is due to the difference
in the moon’s gravitational pulls.
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24. Concept Development 13-3
h. The two blobs will eventually crash into the moon. To orbit around the moon instead of crashing into it, the blobs should move
Then their accelerations will consist of changes in
direction only.
tangentially.
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25. b. This spreading produces
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.
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26. 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
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27. December, June no difference
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
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28. 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
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29. d-R d d+R d = 3.8 x 108 m Mm = 7.34 x 1022 kg mon w = 1 x 106 kg
R = 6.38 x 106 m
mon w = 1 x 106 kg
Fd+R = 3.28 x 101 = 32.8 N
Fd-R = 3.51 x 101 = 35.1 N
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30. Find force of sun on moon 4.366 x 1020 N Find force of earth on moon
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
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31. Satellite Motion 14-1 V = 0.05 km/sec V << 2 km/sec
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32. 2. Satellite Motion v v F F F F v v
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33. a. speed? A b. velocity? A c. momentum? A d. kinetic energy? A
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
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34. That’s all folks!