Chapter 4 ASTR

16) The fact that the Voyager spacecraft continue to speed out of the solar system, even though its rockets have no fuel, is an example of A) Newton's first law of motion. B) Newton's second law of motion. C) Newton's third law of motion. D) the universal law of gravitation. E) none of the above.

Answer: A

42) The orbital period of a geosynchronous satellite is A) 23 hours 56 minutes. B) 24 hours. C) 365.25 days. D) 12 years. E) 26,000 years.

Answer: A

10) What would happen if the Space Shuttle were launched with a speed greater than Earth's escape velocity? A) It would travel away from Earth into the solar system. B) It would travel in a higher orbit around Earth. C) It would take less time to reach its bound orbit. D) It would orbit Earth at a faster velocity. E) It would be in an unstable orbit.

Answer: A

12) Which of the following statements is not one of Newton's laws of motion? A) What goes up must come down. B) The rate of change of momentum of an object is equal to the net force applied to the object. C) In the absence of a net force, an object moves with constant velocity. D) For any force, there always is an equal and opposite reaction force. E) All of the above are Newton's laws of motion.

Answer: A

2) What is the acceleration of gravity of Earth? A) 9.8 m/s2 downward B) 9.8 m/s downward C) 9.8 km/s2 downward D) 9.8 m2/s downward E) 9.8 km/s downward

Answer: A

27) Absolute zero is A) 0° Kelvin. B) 0° Celsius. C) 0° Fahrenheit. D) 32° Fahrenheit. E) 273° Celsius.

Answer: A

30) The amount of gravitational potential energy released as an object falls depends on A) its mass and the distance it falls. B) its mass and its speed at the time it begins falling. C) only the distance it falls. D) only its mass. E) only its speed at the time it begins falling.

Answer: A

33) Which of the following scenarios correctly demonstrates the transformation of mass into energy as given by Einstein's equation, E = mc2? A) When hydrogen is fused into helium, whether in the Sun or in a nuclear bomb, the mass difference is turned into energy. B) An object accelerated to a great speed has a lot of kinetic energy. C) A mass raised to a great height has a lot of gravitational potential energy. D) When you boil a pot of water, it has a high heat content, or thermal energy. E) A burning piece of wood produces light and heat, therefore giving off radiative and thermal energy.

Answer: A

45) According to what we now know from Newton's laws, which of the following best explains why Kepler's second law is true? A) A planet's angular momentum must be conserved as it moves around its orbit. B) Orbits must be elliptical in shape. C) Gravity is an inverse cube law. D) This effect happens because of the influence of other planets on a particular planet's orbit.

Answer: A

48) Which of the following best describes the origin of ocean tides on Earth? A) Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth. B) The Moon's gravity pulls harder on water than on land, because water is less dense than rock. C) Tides are caused by the 23 1/2° tilt of the earth's rotational axis to the ecliptic plane. D) Tides are caused primarily by the gravitational force of the Sun. E) Tides are caused on the side of Earth nearest the Moon because the Moon's gravity attracts the water.

Answer: A

11) Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will A) continue to move in the same way forever, no matter what happens. B) continue to move in the same way until it is acted upon by a force. C) eventually slow down and come to a stop. D) continue to move in a straight line forever if it is in space, but slow and stop otherwise. E) continually slow down but never quite come to a complete stop.

Answer: B

37) When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy? A) The energy goes into the ground and, as a result, the orbit of the earth about the Sun is slightly changed. B) The energy goes to producing sound and to heating the ground, rock, and surrounding air. C) The rock keeps the energy inside it (saving it for later use). D) It is lost forever. Energy does not have to be conserved. E) It is transformed back into gravitational potential energy.

Answer: B

52) Suppose a lone asteroid happens to be passing relatively near Jupiter (but not near any of its moons), following a hyperbolic orbit as it approaches Jupiter. Which of the following statements would be true? A) Jupiter's gravity would capture the asteroid, making it a new moon of Jupiter. B) The asteroid's orbit around Jupiter would not change, and it would go out on the same hyperbolic orbit that it came in on. C) Jupiter would probably expel the asteroid far out into the solar system. D) The asteroid would slowly spiral into Jupiter until it crashed into the atmosphere. E) Any of these scenarios is possible.

Answer: B

15) The movement of a pool ball, after being struck by a cue, is an example of A) Newton's first law of motion. B) Newton's second law of motion. C) Newton's third law of motion. D) the universal law of gravitation. E) conservation of momentum.

Answer: B

18) What quantities does angular momentum depend upon? A) mass and velocity B) mass, velocity, and radius C) force and radius D) force, velocity, and radius E) momentum and angular velocity

Answer: B

23) Gasoline is useful in cars because it has A) gravitational potential energy. B) chemical potential energy. C) electrical potential energy. D) kinetic energy. E) radiative energy.

Answer: B

24) Which of the following is a form of electrical potential energy? A) coal B) energy coming to your house from power companies C) energy from the Sun D) light from a fluorescent bulb E) moving blades on an electric mixer

Answer: B

34) The ultimate source of energy that powers the Sun is A) chemical potential energy of hydrogen burning into helium. B) mass energy of hydrogen fusing into helium. C) gravitational potential energy of the contraction of the gas cloud that formed the Sun. D) kinetic energy of the orbital motion of the Sun. E) thermal energy of the hydrogen atoms in the Sun.

Answer: B

36) Where does the energy come from that your body uses to keep you alive? A) It is produced from the radiative energy of the Sun on your skin. B) It comes from the foods you eat. C) It comes from the water you drink. D) It is in the air that you breathe. E) It is created during the time that you rest or sleep.

Answer: B

38) According to the universal law of gravitation, the force due to gravity is A) directly proportional to the square of the distance between objects. B) inversely proportional to the square of the distance between objects. C) directly proportional to the distance between objects. D) inversely proportional to the distance between objects. E) not dependent on the distance between objects.

Answer: B

4) Momentum is defined as A) mass times speed. B) mass times velocity. C) force times velocity. D) mass times acceleration. E) force times acceleration.

Answer: B

47) The mass of Jupiter can be calculated by A) measuring the orbital period and distance of Jupiter's orbit around the Sun. B) measuring the orbital period and distance of one of Jupiter's moons. C) measuring the orbital speed of one of Jupiter's moons. D) knowing the Sun's mass and measuring how Jupiter's speed changes during its elliptical orbit around the Sun. E) knowing the Sun's mass and measuring the average distance of Jupiter from the Sun.

Answer: B

53) A basketball player jumps to make a basket, and remains in the air for a moment. A sportscaster, talking about the game, then remarks that she has "defied gravity." Which of the following accurately describes the situation? A) The player did stay in the air in spite of the Law of Gravitation, but a single counter-observation is not enough to warrant revisiting a theory that usually works. B) The player produced enough force with her legs to accelerate up into the air, and gravity brought her back down with an acceleration of 9.8 m/s2. C) The player only seemed to defy gravity, but part of the Universal Law of Gravitation makes an exception for basketball players. D) The player has defied gravity, so scientists must go back into the lab to refine their theory.

Answer: B

54) Imagine we've discovered a planet orbiting another star at 1 AU every 6 months. The planet has a moon that orbits the planet at the same distance as our Moon, but it takes 2 months. What can we infer about this planet? A) It is more massive than Earth. B) It is less massive than Earth. C) It has the same mass as Earth. D) We cannot answer the question without knowing the mass of the star. E) We cannot answer the question without knowing the mass of the moon.

Answer: B

1) Which of the following is an example in which you are traveling at constant speed but not at constant velocity? A) rolling freely down a hill in a cart, traveling in a straight line B) driving backward at exactly 50 km/hr C) driving around in a circle at exactly 100 km/hr D) jumping up and down, with a period of exactly 60 hops per minute E) none of the above

Answer: C

17) Changing the orbit of a spacecraft by firing thrusters is an example of A) Newton's first law of motion. B) Newton's second law of motion. C) Newton's third law of motion. D) the universal law of gravitation. E) none of the above.

Answer: C

22) Radiative energy is A) heat energy. B) energy from nuclear power plants. C) energy carried by light. D) energy used to power home radiators. E) energy of motion.

Answer: C

25) Which object has the most kinetic energy? A) a 4-ton truck moving 50 km/hr B) a 3-ton truck moving 70 km/hr C) a 2-ton truck moving 90 km/hr D) a 1-ton truck moving 110 km/hr E) A, B, C, and D all have the same kinetic energy.

Answer: C

26) Of the temperature ranges below, which range represents the smallest range of actual temperature? A) 50-100° Kelvin B) 50-100° Celsius C) 50-100° Fahrenheit D) They all represent the same change in temperature.

Answer: C

28) What does temperature measure? A) the average mass of particles in a substance B) the average size of particles in a substance C) the average kinetic energy of particles in a substance D) the total number of particles in a substance E) the total potential energy of particles in a substance

Answer: C

32) Considering Einstein's famous equation, E = mc2, which of the following statements is true? A) Mass can be turned into energy, but energy cannot be turned back into mass. B) It takes a large amount of mass to produce a small amount of energy. C) A small amount of mass can be turned into a large amount of energy. D) You can make mass into energy if you can accelerate the mass to the speed of light. E) One kilogram of mass represents 1 joule of energy.

Answer: C

35) Which of the following statements correctly describes the law of conservation of energy? A) An object always has the same amount of energy. B) Energy can change between many different forms, such as potential, kinetic, and thermal, but it is ultimately destroyed. C) The total quantity of energy in the universe never changes. D) The fact that you can fuse hydrogen into helium to produce energy means that helium can be turned into hydrogen to produce energy. E) It is not really possible for an object to gain or lose potential energy, because energy cannot be destroyed.

Answer: C

39) The force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them A) also doubles. B) strengthens by a factor of 4. C) weakens by a factor of 4. D) weakens by a factor of 2. E) is unaffected.

Answer: C

43) The allowed shapes for orbits under the force of gravity are A) ellipses only. B) ellipses and spirals. C) ellipses, parabolas, and hyperbolas. D) ellipses, spirals, and parabolas. E) spirals, circles, and squares.

Answer: C

5) If an object's velocity is doubled, its momentum is A) halved. B) unchanged. C) doubled. D) quadrupled. E) dependent on its acceleration.

Answer: C

9) You are standing on a scale in an elevator. Suddenly you notice your weight decreases. What do you conclude? A) The elevator is accelerating upwards. B) The elevator is moving at a constant velocity upwards. C) The elevator is accelerating downwards. D) The elevator is moving at a constant velocity downwards. E) Your diet is working.

Answer: C

21) Which of the following is not a unit of energy? A) Calorie B) joule C) calorie D) kilowatt E) British thermal unit

Answer: D

14) How does the Space Shuttle take off? A) Its rocket engines push against the launch pad propelling the shuttle upwards. B) It converts mass-energy to kinetic energy. C) It achieves lift from its wings in the same way that airplanes do. D) Hot gas shoots out from the rocket and, by conservation of momentum, the shuttle moves in the opposite direction. E) The hot rocket exhaust expands the air beneath the shuttle, propelling it forward.

Answer: D

19) A skater can spin faster by pulling her arms closer to her body or spin slower by spreading her arms out from her body. This is due to A) the law of gravity. B) Newton's third law. C) conservation of momentum. D) conservation of angular momentum. E) conservation of energy.

Answer: D

20) Which of the following is not a conserved quantity? A) energy B) momentum C) angular momentum D) radiation

Answer: D

31) In the formula E = mc2, what does E represent? A) the kinetic energy of a moving object B) the radiative energy carried by light C) the gravitational potential energy of an object held above the ground D) the mass-energy, or potential energy stored in an object's mass E) the electric charge of the object

Answer: D

41) According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will A) not change at all. B) increase by a factor of 2. C) decrease by a factor of 2. D) increase by a factor of 4. E) decrease by a factor of 4.

Answer: D

44) Each of the following lists two facts. Which pair can be used with Newton's version of Kepler's third law to determine the mass of the Sun? A) Mercury is 0.387 AU from the Sun, and Earth is 1 AU from the Sun. B) The mass of Earth is 6 × 1024 kg, and Earth orbits the Sun in 1 year. C) Earth rotates in 1 day and orbits the Sun in 1 year. D) Earth is 150 million km from the Sun and orbits the Sun in 1 year. E) Jupiter is the most massive planet and has a mass of 1.9 × 1027 kg.

Answer: D

46) The center of mass of a binary star system is A) the center of the most massive of the two stars. B) the center of the least massive of the two stars. C) the point halfway in between them. D) the point at which the two objects would balance if they were somehow connected. E) the average mass of the two stars.

Answer: D

49) The tides on Earth are an example of A) Newton's first law of motion. B) Newton's second law of motion. C) Newton's third law of motion. D) the universal law of gravitation. E) none of the above

Answer: D

50) At which lunar phase(s) are tides most pronounced (e.g., the highest high tides)? A) first quarter B) new Moon C) full Moon D) both new and full Moons E) both first and third quarters

Answer: D

7) If your mass is 60 kg on Earth, what would your mass be on the Moon? A) 10 lb B) 10 kg C) 50 kg D) 60 kg E) 60 lb

Answer: D

8) In which of the following cases would you feel weightless? A) while walking on the Moon B) while falling from an airplane with your parachute open C) while traveling through space in an accelerating rocket D) while falling from a roof E) none of the above

Answer: D

13) Newton's second law of motion tells us that the net force applied to an object equals its A) mass times energy. B) momentum times velocity. C) mass times velocity. D) energy times acceleration. E) mass times acceleration.

Answer: E

29) Suppose you heat up an oven and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven? A) The oven has a higher temperature than the water. B) The water has a higher temperature than the oven. C) The oven has a higher heat content than the water. D) The molecules in the water are moving faster than the molecules in the oven. E) The water has a higher heat content than the oven.

Answer: E

3) If you drop a rock from a great height, about how fast will it be falling after 5 seconds, neglecting air resistance? A) It depends on how heavy it is. B) It depends on what shape it is. C) 10 m/s D) 15 m/s E) 50 m/s

Answer: E

40) According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will A) increase by a factor of 3. B) decrease by a factor of 3. C) decrease by a factor of 6. D) increase by a factor of 9. E) decrease by a factor of 9.

Answer: E

51) At which lunar phase(s) are tides least pronounced (e.g., the lowest high tides)? A) first quarter B) new Moon C) full Moon D) both new and full Moons E) both first and third quarters

Answer: E

6) As long as an object is not gaining or losing mass, a net force on the object will cause a change in A) acceleration. B) direction. C) weight. D) speed. E) velocity.

Answer: E

1) Speed and velocity are the same thing.

Answer: FALSE

10) The escape velocity from Earth is greater for larger rockets than for small ones.

Answer: FALSE

14) Process of Science: Gravity only affects very massive objects and we can therefore only test theories about it when looking at the orbits of planets.

Answer: FALSE

4) If you double the mass of fusion material in a hydrogen bomb, you quadruple the amount of energy generated.

Answer: FALSE

5) When energy is converted from one form to another, a tiny amount is inevitably lost.

Answer: FALSE

6) Kepler deduced his laws of planetary motion once Newton had published his universal law of gravitation.

Answer: FALSE

8) There is no gravity in space.

Answer: FALSE

9) Doubling the distance between two objects halves the gravitational force between them.

Answer: FALSE

11) Tidal friction caused by Earth's stretching from the Moon's gravity is gradually slowing down the rotation of Earth.

Answer: TRUE

12) The Moon is slowly moving away from Earth.

Answer: TRUE

13) Unbound orbits have more orbital energy than bound orbits.

Answer: TRUE

2) The Moon is constantly falling toward Earth.

Answer: TRUE

3) If you are driving at 30 miles per hour and increase your speed to 60 miles per hour, you quadruple your kinetic energy.

Answer: TRUE

7) The center of mass for Earth orbiting the Sun lies inside the Sun.

Answer: TRUE