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

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

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

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

Demo Distorted Room

Distorted Room or . . .

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

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

Demo Sun-Earth-Moon

Sun Earth Moon Allignment

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

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

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

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

CD 13-1 p52

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

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 CD 13-1 p51

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

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. CD 13-1 p55

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

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

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

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. CD 13-1 p55

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. CD 13-1 p55

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

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 CD 13-1 p55

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

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 CD 13-1 p56

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 CD 13-1 p56

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

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

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 CD 13-1 p58

That’s all folks!