Chapter 4

T/F The Moon is constantly falling toward Earth.

T

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.

B

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.

B

Newton's version of Kepler's third law states: p2 = × a3 According to this, what observational information does one need in order to calculate the combined mass of a planet and its moon? A) the orbital period and the density of the two objects B) the average distance between the two objects and the orbital period C) the radius of the two planets in meters and the average distance between them D) It is impossible to determine the mass of any astronomical object.

B

Newton's version of Kepler's third law states: p2 = × a3 In this equation, what does a represent? A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant

B

Suppose an object is moving in a straight line at 50 mi/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 fall to the ground if it is on Earth.

B

The force due to gravity between two objects can be described using the equation Fg = G M1 M2 / d2. According to this equation, if the distance between two objects increases, what happens to the gravitational force between them? A) The force increases. B) The force decreases. C) The force drops instantly to zero. D) The gravitational force is not affected by distance.

B

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.

B

The speed at which a pool ball moves after being struck by a cue is most directly 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.

B

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.

B

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

B

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.

B

T/F Doubling the distance between two objects halves the gravitational force between them.

F

T/F If you double the mass of fusion material in a hydrogen bomb, you quadruple the amount of energy generated.

F

T/F Kepler deduced his laws of planetary motion once Newton had published his universal law of gravitation.

F

T/F Planets with larger orbital radii have longer orbital periods because they both have a longer distance to travel in each orbit and move more slowly.

F

T/F Speed and velocity are the same thing.

F

T/F The escape velocity from Earth is greater for larger rockets than for small ones.

F

T/F There is no gravity in space.

F

T/F When energy is converted from one form to another, a tiny amount is inevitably lost.

F

T/F When you experience a downward gravitational force from the Earth, the Earth experiences a weaker upward gravitational force from you.

F

T/F Planets with larger orbital radii have longer orbital periods only because they have a longer distance to travel in each orbit.

T

T/F The Moon is slowly moving away from Earth.

T

T/F Tidal friction caused by Earth's stretching from the Moon's gravity is gradually slowing down the rotation of Earth.

T

T/F To measure the mass of an astronomical object, one can observe the orbital period and distance of a companion.

T

T/F Unbound orbits have more orbital energy than bound orbits.

T

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 total orbital energy 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.

A

Newton's second law states: sum of forces = mass × acceleration. According to this, what property can you determine if you observe the acceleration of an object with a known mass? A) the sum total of all forces acting on the object B) the value of a single force acting on the object C) the current velocity of the object. D) the current location of the object

A

Newton's version of Kepler's third law states: p2 = × a3 In this equation, what does p represent? A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant

A

The amount of gravitational potential energy released as an object falls depends on A) the distance it falls. B) its speed at the time it begins falling. C) the distance it falls and its speed at the time it begins falling. D) neither the distance it falls nor its speed at the time it begins falling.

A

The fact that Voyager 10 continues 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

A

The force due to gravity between two objects can be described using the equation Fg = G M1 M2 / d2. According to this equation, if the mass of the second object were greater, what happens to the gravitational force between them? A) The force increases. B) The force decreases. C) The force drops instantly to zero. D) The gravitational force is not affected by the mass of the second object.

A

The force due to gravity between two objects can be described using the equation Fg = G M1 M2 / d2. In this equation, what does G represent? A) the universal gravitational constant B) the density of the smaller object C) the distance between the two objects

A

The force due to gravity between two objects can be described using the equation Fg = G M1 M2 / d2. In this equation, what does M1 represent? A) the mass of one of the objects B) the distance, in meters, between the two objects C) the diameter, in meters, of one of the objects

A

What is the acceleration of gravity at the surface 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

A

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.

A

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.

E

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

C

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.

C

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

C

Newton's second law states: sum of forces = mass × acceleration. If a known force was applied to an object with a known mass, how would you predict that object's acceleration? A) acceleration = mass × sum of forces B) acceleration = mass / sum of forces C) acceleration = sum of forces / mass D) Newton's second law is irrelevant for solving this problem.

C

Newton's version of Kepler's third law states: p2 = × a3 In this equation, what do M1 and M2 represent? A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant

C

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.

C

The force due to gravity between two objects can be described using the equation Fg = G M1 M2 / d2. In this equation, what does d represent? A) the universal gravitational constant B) the density of the smaller object C) the distance between the two objects

C

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.

C

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.

C

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.

C

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.

D

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

E

How does the Space Shuttle take off? A) Its rocket engines push against the launch pad, propelling the shuttle upwards. B) by converting mass-energy to kinetic energy C) by achieving 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.

D

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

D

Newton's version of Kepler's third law states: p2 = × a3 In this equation, what does G represent? A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant

D

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

D