Chapter 5 Review

11. The gravitational attraction of the Sun for Earth is ____ that of Earth for the Sun. A. the same as B. greater than C. smaller than

A

12. What is the acceleration due to Earth's gravity at a distance of one Earth radius above Earth's surface? A. 2.5 m/s2 B. 5 m/s2 C. 10 m/s2 D. 20 m/s2

A

14. An astronaut weighs 900 N when measured on the surface of Earth. How large would the force of gravity on him be if he were in an Earth satellite at an altitude equal to Earth's radius? A. 225 N B. 450 N C. 900 N D. 3600 N

A

26. A solid lead sphere of radius 10 m (about 66 ft across!) has a mass of about 57 million kg. If two of these spheres are floating in deep space with their centers 20 m apart, the gravitational attraction between the spheres is only 540 N (about 120 lb). How large would this gravitational force be if the distance between the centers of the two spheres were tripled? A. 60 N B. 180 N C. 1620 N D. 4860 N

A

36. If an astronaut with a weight of 800 N on Earth steps on a bathroom scale while he is in Earth orbit, the scale will read A. zero. B. less than 800 N. C. 800 N. D. more than 800 N.

A

38. From film taken in SkyLab and the Space Shuttle, we learned that objects in SkyLab A. have mass but no weight. B. have mass but no force due to gravity. C. have neither mass nor weight. D. fall to the floor with an acceleration of 9.5 m/s2.

A

46. Exhibit 5-1 Sally is an astronaut who has a mass of 60 kg. Currently she is conducting experiments in a permanent space station that is orbiting Earth at an altitude equal to Earth's radius. Refer to Exhibit 5-1. What is Sally's weight in the space station? A. zero B. 150 N C. 300 N D. 600 N

A

47. The highest high tides and the lowest low tides occur when the Moon is A. full or new. B. full only. C. new only. D. first and third quarter.

A

49. Which of the following celestial bodies has the greatest influence on Earth's tides? A. Moon B. Sun C. Venus D. Jupiter

A

50. Jupiter rotates about its axis once every 10 hours. How much time passes between high tides in its atmosphere? A. 5 hrs B. 10 hrs C. 20 hrs D. 100 hrs

A

51. Mercury orbits the sun about once every 80 days. Mercury is observed to keep the same side facing the sun at all times. If Mercury had oceans, how much time would elapse between its high tides A. there would be no tides B. 40 days C. 80 days D. 160 days

A

54. Suppose that the planet Mercury were magically replaced with a baseball. The magnitude of the acceleration of the baseball would be A. equal to that of Mercury B. greater than that of Mercury C. less than that of Mercury

A

55. Suppose that the planet Mercury were magically replaced with a baseball. The magnitude of the net force exerted on the baseball would be A. equal to that exerted on Mercury B. greater than that exerted on Mercury C. less than that exerted on Mercury

A

59. On the surface of a certain planet, the gravitaional field strength has numerical value 5.2. This means that A. an object of mass 1 kg will experience a gravitational force of 5.2 newtons B. an object must have a mass of 5.2 kg in order to experience a gravitational force of 1 newton

A

62. Exhibit 5-2 On the surface of a certain planet, there is one unit of gravitational force exerted on every 0.4 units of mass. Refer to Exhibit 5-2. Suppose that an object on the surface of this planet experiences a force of magnitude F. The mass of this object is A. 0.4*F B. 0.4/F C. F/0.4

A

71. The masses of the Moon and Earth are 7.4 ´ 1022 kg and 6 ´ 1024 kg, respectively. Earth-Moon distance is 3.8 ´ 108 m. What is the size of the gravitational force between Earth and the Moon? The gravitational constant is G = 6.67 ´ 10-11 N-m2/kg2. A. 2.05 ´ 1020 N B. 7.79 ´ 1028 N C. 3.07 ´ 1030 N D. 1.17 ´ 1039 N

A

75. An 90-kg satellite orbits a distant planet with a radius of 4000 km and a period of 280 min. From the radius and period, you calculate the satellite's acceleration to be 0.56 m/s2. What is the gravitational force on the satellite? A. 50.4 N B. 90 N C. 720 N D. 12,000 N

A

8. Which of the following forces are exerted on a satellite that is in orbit around Earth? A. an attractive gravitational force directed toward the center of Earth B. a force in the direction of the satellite's motion C. an outward force directed away from the center of Earth D. a and b

A

17. If you double the length of each side of a cube, its surface area increases by what factor? A. 2 B. 4 C. 6 D. 8

B

19. If you double the radius of a sphere, its surface area increases by what factor? A. 2 B. 4 C. 6 D. 8

B

2. The discussion of the "launched apple" and the Moon shows that the A. velocities of the apple and Moon are constant. B. motion of the Moon and apple can be explained by the same laws. C. apple and the Moon have the same acceleration. D. apple and the Moon experience the same-sized force.

B

35. Earth exerts a gravitational force of 7000 N on one of the communications satellites. What force does the satellite exert on Earth? A. more than 7000 N B. 7000 N C. less than 7000 N D. zero

B

37. Al the astronaut has a mass of 90 kg and a weight of 900 N when he is standing on Earth's surface. What is his mass when he is in a space station orbiting Earth with a radius of three Earth radii? A. zero B. 90 kg C. 30 kg D. 10 kg

B

43. Communications satellites are synchronous satellites that orbit Earth each A. 90 minutes B. 24 hours C. 28 days D. They don't orbit Earth, they just stay in one place.

B

45. Exhibit 5-1 Sally is an astronaut who has a mass of 60 kg. Currently she is conducting experiments in a permanent space station that is orbiting Earth at an altitude equal to Earth's radius. Refer to Exhibit 5-1. What is the force of gravity acting on Sally while she is in the space station? A. zero B. 150 N C. 300 N D. 600 N

B

57. For simplicity, a professor uses 9.8 (meters per second) per second for the acceleration due to gravity instead of the more precise 9.81 (meters per second) per second. If Cavendish had made the same approximation, his estimate for Earth's mass have been A. too high B. too low

B

60. On the surface of a certain planet, the gravitaional field strength has numerical value gplanet. An object that experiences a gravitational force of 0.7 newtons on this planet must have a mass of A. 0.7*gplanet B. 0.7/gplanet C. gplanet/0.7

B

64. If Earth's mass were suddenly and magically reduced to half its present value, the Sun's gravitational force on Earth would A. be reduced by a factor of 4. B. be reduced by a factor of 2. C. remain the same. D. increase by a factor of 2.

B

65. An astronomer discovers a new planet orbiting a distant star. By measuring the size of the orbit and the time for the planet to complete one trip around the star, the astronomer can infer A. the mass of the planet B. the mass of the star C. both a and b D. neither a nor b

B

67. The gravitational force between two very large metal spheres in outer space is 200 N. How large would this force be if the mass of each sphere were cut in half? A. 12.5 N B. 50 N C. 100 N D. 200 N

B

68. A 320-kg satellite experiences a gravitational force of 800 N. What is the radius of the satellite's orbit? (Earth's radius is 6,400 km.) A. 6,400 km B. 12,800 km C. 19,200 km D. 25,600 km

B

74. Mercury has a radius of about 0.38 Earth radii and a mass of only 0.055 Earth masses. Estimate the acceleration due to gravity on Mercury. A. 1.45 m/s2 B. 3.81 m/s2 C. 26.3 m/s2 D. 69.1 m/s2

B

9. The size of the gravitational force that Earth exerts on the Moon is ____ that the Moon exerts on Earth. A. greater than B. the same as C. smaller than

B

10. Earth is held in its orbit by the gravitational force of the Sun. Therefore, the force that the Sun exerts on Earth is ____ that Earth exerts on the Sun. A. greater than B. smaller than C. the same as

C

13. What is the acceleration due to Earth's gravity at a distance of 10 Earth radii from Earth's center? A. 10 m/s2 B. 1 m/s2 C. 0.1 m/s2 D. 0.01 m/s2

C

20. A future space traveler, Skip Parsec, lands on the planet MSU3, which has the same mass as Earth but twice the radius. If Skip weighs 800 N on Earth's surface, how much does he weigh on MSU3's surface? A. 50 N B. 100 N C. 200 N D. 400 N

C

21. Astronaut Skip Parsec visits planet MSU8, which is composed of the same materials as Earth, but has twice the radius. If Skip weighs 800 N on Earth's surface, how much does he weigh on MSU8's surface? A. 400 N B. 800 N C. 1600 N D. 3200 N

C

22. In the law of universal gravitation the force ____ as the mass increases and ____ as the distance increases. A. increases ... increases B. decreases ... increases C. increases ... decreases D. decreases ... Decreases

C

25. The gravitational force between two metal spheres in outer space is 1000 N. How large would this force be if each of the two spheres had twice the mass? A. 1000 N B. 2000 N C. 4000 N D. 16,000 N

C

28. Does the Moon orbit the Sun? A. Yes. It goes in a circle about the Sun. B. No. It orbits Earth. C. Yes, but it also orbits Earth. D. No, but it would if Earth were not present.

C

29. During the Apollo flights to the Moon a well-known TV newscaster made the following statement, "The Apollo space craft is now leaving the gravitational force of Earth." This statement is incorrect. He should have said that the space craft A. was attracted only by the Moon. B. was attracted only by the Sun C. was attracted more by the Moon than by Earth. D. entered a region of space where there were no gravitational forces.

C

32. When Cavendish claimed that he "weighed" Earth, he actually calculated the A. force that the Moon exerts on Earth. B. weight of Earth. C. mass of Earth. D. force that the Sun exerts on Earth.

C

40. NASA uses the famous "Vomit Comet," a KC-135 cargo plane, to provide astronauts and scientiest a simulated zero-gravity environment. The plane flies in a parabolic arc, at the top of which a passenger feels "weightless." This is because A. the acceleration of the passenger is nearly zero at the top of the arc B. the gravitational force exerted by Earth on the passenger is nearly zero at the top of the arc C. the force exerted by the floor of the plane on the passenger is nearly zero at the top of the arc D. a and b

C

56. In a parallel universe, there is a planet with the same mass and radius as Earth. However, when an apple is dropped on this planet, it fall with an acceleration of 5 (meters per second) per second. The value of G in this parallel universe is A. the same as it is in our universe B. twice as large as it is in our universe C. half as large as it is in our universe D. four times as large as it is in our universe

C

58. Given that the acceleration due to gravity on Mars is 3.7 m/s2, what is the gravitational field near Mar's surface? A. 3.7 N/kg B. 3.7 N/kg up C. 3.7 N/kg down D. 10 N/kg down

C

61. Exhibit 5-2 On the surface of a certain planet, there is one unit of gravitational force exerted on every 0.4 units of mass. Refer to Exhibit 5-2. The gravitational field strength on this planet has numerical value A. 1 B. 0.4 C. 2.5

C

63. Exhibit 5-2 On the surface of a certain planet, there is one unit of gravitational force exerted on every 0.4 units of mass. Refer to Exhibit 5-2. Suppose that an object on the surface of this planet has mass M. The gravitation force exerted on this object is A. 0.4*M B. 0.4/M C. M/0.4

C

66. If Earth's mass were suddenly and magically reduced to half its present value, the magnitude of Earth's acceleration about the Sun would A. be reduced by a factor of 4. B. be reduced by a factor of 2. C. remain the same. D. increase by a factor of 2.

C

69. A 600-kg geosynchronous satellite has an orbital radius of 6.6 Earth radii. What gravitational force does Earth exert on the satellite? A. 13.8 N B. 90.9 N C. 138 N D. 909 N

C

72. If an astronaut in full gear has a weight of 1200 N on Earth, how much will the astronaut weigh on the Moon? A. 20 N B. 120 N C. 200 N D. 720 N

C

73. The acceleration due to gravity on Titan, Saturn's largest Moon, is about 1.4 m/s2. What would a 60-kg scientific instrument weigh on Titan? A. 43 N B. 60 N C. 84 N D. 600 N

C

1. What force drives the planets along their orbits? A. gravity B. magnetism C. solar wind D. No force is needed to drive them along their orbits.

D

15. Al the astronaut has a weight of 800 N when he is standing on the surface of Earth. What is the force of gravity acting on him when he is in a space station orbiting Earth at a distance of three Earth radii above the surface? A. 800 N B. 200 N C. 100 N D. 50 N

D

16. If you double the length of each side of a cube, its volume increases by what factor? A. 2 B. 4 C. 6 D. 8

D

18. If you double the radius of a sphere, its volume increases by what factor? A. 2 B. 4 C. 6 D. 8

D

23. The gravitational force between two metal spheres in outer space is 2000 N. How large would the force be if the two spheres were four times as far apart? A. 32,000 N B. 8000 N C. 500 N D. 125 N

D

24. The gravitational force between two metal spheres in outer space is 1800 N. How large would the force be if the two spheres were twice as far apart? A. 7200 N B. 3600 N C. 900 N D. 450 N

D

27. Two spacecraft in outer space attract each other with a force of 20 N. What would the attractive force be if they were one-half as far apart? A. 5 N B. 10 N C. 40 N D. 80 N

D

3. If we imagine launching an apple into a circular orbit about Earth and ignore the effects of air resistance, we know that the apple will experience A. a constant velocity. B. no net force. C. a force due to its inertia. D. a centripetal force due to gravity.

D

30. The numerical value of G, the gravitational constant, was determined A. from knowledge of Earth's mass. B. from the law of universal gravitation and the value of the acceleration due to gravity. C. from the value of the Moon's acceleration. D. by measuring the force between masses in the laboratory.

D

31. The gravitational constant G in the law of universal gravitation A. is believed to be constant with time. B. is believed to have the same value throughout space. C. leads to a determination of the mass of Earth. D. All of the above are true.

D

33. The law of universal gravitation is written F = GMm/r2. Why did we use the form F = mg when we studied projectile motion? A. The first form is not valid for projectile motion. B. The first form does not work because it requires two masses. C. The first form is not valid near the surface of Earth. D. The second form is a good approximation to the first and much simpler to use.

D

34. Which of the following would NOT cause the gravitational force on an object near Earth's surface to increase? A. an ore deposit just under the surface B. a lower elevation C. an increase in its mass D. a horizontal velocity

D

39. You are standing on a bathroom scale in an elevator that is moving upward at constant speed, when suddenly the cable breaks. From just before to just after the cable breaks, the reading on the scale A. increases by a little bit B. decreases by a little bit C. remains the same D. decreases to zero

D

4. Which of the following statements about the Moon is correct? A. The Moon has a constant velocity. B. There is no net force acting on the Moon. C. Earth exerts a stronger force on the Moon than the Moon exerts on Earth. D. The Moon experiences a centripetal acceleration toward Earth.

D

41. A child takes a small plastic bucket full of water and swings the bucket over her head in a circular arc, just barely fast enough for the water to stay in the bucket. Unbeknownst to the child, a fish is in the middle of the water. At the top of the arc, the fish A. has a downward acceleration B. feels "weightless" C. has zero net force acting on it D. a and b

D

42. Over which of the following locations is it possible to have a synchronous satellite? A. New York City B. Los Angeles C. North Pole D. equator

D

44. Exhibit 5-1 Sally is an astronaut who has a mass of 60 kg. Currently she is conducting experiments in a permanent space station that is orbiting Earth at an altitude equal to Earth's radius. Refer to Exhibit 5-1. What is Sally's mass as measured in the space station? A. zero B. 15 kg C. 30 kg D. 60 kg

D

48. In a typical 24 hour day, there are A. one high tide and one low tide. B. one high tide and two low tides. C. two high tides and one low tide. D. two high tides and two low tides.

D

5. Which of the following statements about Venus is correct? A. Venus has a constant velocity. B. There is no net force acting on Venus. C. The Sun exerts a stronger force on Venus than Venus exerts on the Sun. D. Venus is continually accelerating toward the Sun.

D

52. Although Earth's gravitational influence gets weaker with distance, we believe that it extends as far as the A. Sun. B. edge of the solar system. C. edge of the galaxy. D. universe extends.

D

53. What is the magnitude of Earth's gravitational field at a distance equal to twice Earth's radius? A. 20 N/kg B. 10 N/kg C. 5 N/kg D. 2.5 N/kg

D

6. Which of the following statements about the Moon is not correct? A. The acceleration due to gravity on the Moon is weaker than on Earth. B. Earth's gravitational pull on the Moon equals the Moon's gravitational pull on Earth. C. There is a net force acting on the Moon. D. The Moon is not accelerating.

D

7. Which of the following statements about Venus is not correct? A. The Sun's gravitational pull on Venus equals Venus' gravitational pull on the Sun. B. There is a net force acting on Venus. C. Venus is accelerating toward the Sun. D. There is no gravity on the surface of Venus.

D

70. What is the gravitational force between two 20-kg iron balls separated by a distance of 0.5 m? The gravitational constant is G = 6.67 ´ 10-11 N-m2/kg2. A. 2.67 ´ 10-9 N B. 5.34 ´ 10-9 N C. 5.34 ´ 10-8 N D. 1.07 ´ 10-7 N

D