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Homework 20-23

# Homework 20-23 - Homework 20 Answer Conceptual Question...

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Homework 20: Answer Conceptual Question Chap 7: 4 and 6 40 pts Solve Problems Chap 7: 29, 36 Conceptual Questions CQ 7: 4 Explain why Earth is not spherical in shape, but bulges at the equator. Answer: The need for a large force toward the center of the circular path on objects near the equator will  cause the Earth to bulge at the equator. A force toward the center of the circular path is not  needed at the poles, so the radius in this direction will be smaller than at the equator. CQ 7.6 At night, you are farther away from the sun than during the day. What's more, the force exerted by the Sun on you is downward into Earth at night, and upward into the sky during the day. If you had a sensitive enough bathroom scale, would you appear to weight more at night than during the day? Answer : To a good first approximation, your bathroom scale reading is unaffected because you, Earth,  and the scale are all in free fall in the Sun’s gravitational field, in orbit around the Sun. To a  precise second approximation, you weight slightly less at noon and at midnight than you do at  sunrise or sunset. The Sun’s gravitational fields is a little weaker at the center of the Earth than  at the surface sub-solar point, and a little weaker still on the far side of the planet. When the Sun  is high in your sky, its gravity pulls up on you a little more strongly than on the Earth as a whole.  At midnight the Sun pulls down on you a little less strongly than it does on the Earth below you.  So you can have another doughnut with lunch, and your bedsprings will still last a little longer.

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Problems Prob 7. 29 The average distance separating the Earth and moon is 384000 km. Use the data in Table 7.3 to find the net gravitation force exerted by Earth and the Moon on a 3000 kg spaceship located halfway between them. Solution: At the half-way point the spaceship is 8 1.92 10  m × from both bodies. The force exerted on the ship by the Earth is directed toward the Earth and has magnitude ( 29 ( 29 ( 29 ( 29 2 11 2 2 24 4 2 8 6.67 10   N m kg 5.98 10  kg 3.00 10  kg 325 N 1.92 10  m E s E Gm m F r - = × × × = = × The force exerted on the ship by the Moon is directed toward the Moon and has a magnitude of ( 29 ( 29 ( 29 ( 29 2 11 2 2 22 4 2 8 6.67 10   N m kg 7.36 10  kg 3.00 10  kg 4.00 N 1.92 10  m M s M Gm m F r - = × × × = = × The resultant force is ( 29 325 N 4.00 N 321 N directed toward Earth - = . Prob 7.36 A 600 kg satellite is in a circular orbit about Earth at a height above Earth equal to Earth's mean radius. Find a) the satellites' orbital speed, b) the period of its revolution and c) the gravitational force acting on it.
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Homework 20-23 - Homework 20 Answer Conceptual Question...

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