Deck 4: Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Question 1

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 1

C

Question 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 2

A

Question 3

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 3

C

Question 4

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.

Question 5

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.

Question 6

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.

Question 7

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.

Question 8

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.

Question 9

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

Question 10

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.

Question 11

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.

Question 12

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

Question 13

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.

Question 14

If an object's velocity is doubled, its momentum is

A) halved.
B) unchanged.
C) doubled.
D) quadrupled.
E) dependent on its acceleration.

Question 15

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.

Question 16

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.

Question 17

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.

Question 18

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

Question 19

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.

Question 20

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.

Question 21

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.

Question 22

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

Question 23

Argument by Analogy: A friend of yours is convinced of the influence of the Moon on everyday human affairs. He cites a supposed correlation between crime and the occurrence of a full moon as proof. He even speculates that the gravitational influence of the Moon is the mechanism by noting that it is the gravitational pull of the Moon that causes the tides. "After all", he argues, "as over half a human's weight is water, the Moon must affect the flow of blood in human beings!" How would you explain to your friend that this analogy, between the ocean tides and water in the human body, is profoundly flawed. Are there any alternate explanations for a link between moon phase and crime?

Question 24

Unbound orbits have more orbital energy than bound orbits.

Question 25

There is no gravity in space.

Question 26

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

Question 27

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

Question 28

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.

Question 29

Hallmarks of a Scientific Theory: All great scientific theories explain existing observations, unify and extend existing concepts, and make new and novel predictions that can be experimentally tested. Using Newton's postulate of universal gravitation as a case study, explicitly demonstrate how it satisfies each of these criteria.

Question 30

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.

Question 31

The Moon is constantly falling toward Earth.

Question 32

Do Things We Cannot Directly Detect Exist? In the early part of the 20th century, physicists experimentally discovered that a certain type of radioactive decay did not seem to conserve either energy or momentum. These experiments were "explained" by postulating the existence of an undetected (and potentially undetectable) particle, dubbed the neutrino, that carried away the missing energy and momentum. It was argued that neutrinos interacted so weakly with matter that they were extremely hard to detect. If you were a scientist at this time, how would you evaluate the reasonableness this solution given Occam's razor?

Question 33

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.

Question 34

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

Question 35

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

Question 36

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

Question 37

The Moon is slowly moving away from Earth.

Question 38

Speed and velocity are the same thing.

Question 39

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

Question 40

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

Question 41

Briefly explain why Earth feels a greater tidal force from the Moon than from the Sun, even though it feels a greater gravitational force from the Sun.

Question 42

Give an example in which thermal energy might be converted to gravitational energy.

Question 43

A planet is orbiting a star. Which of the following statements is true for the acceleration and gravitational forces experienced by the star and the planet?

A) The acceleration of the planet is much more than the acceleration of the star, but the force on the star is the same but opposite the force on the planet.
B) The force on the star is much smaller than the force on the planet, but the accelerations are about equal.
C) The acceleration of the planet is much more than the acceleration of the star, and the force on the planet is much more than the force on the star.

Question 44

State Newton's three laws of motion.

Question 45

Give an example in which kinetic energy can be converted to thermal energy.

Question 46

If a gas cloud shrinks its gravitational potential energy is converted into

A) chemical energy.
B) only radiative energy.
C) kinetic energy and sound waves.
D) thermal energy and radiative energy.

Question 47

Imagine another solar system, with a star of the same mass as the Sun. Suppose there is a planet in that solar system with a mass double that of Earth orbiting at a distance of 1 AU from the star. Thinking about Newton's version of Kepler's third law, what (approximately) is the orbital period of this planet? Explain your answer.

Question 48

Consider the elliptical orbit of a comet around the Sun. Where in its orbit does it have the largest amount of total orbital energy?

A) When it is farthest from the Sun
B) It always has the same total orbital energy.
C) When it is closest to the Sun

Question 49

Under what conditions is an object weightless?

Question 50

Suppose it takes 6 seconds for a watermelon to fall to the ground after being dropped from a tall building. If there were no air resistance, so that the watermelon would fall with the acceleration of gravity, about how fast would it be going when it hit the ground?

Question 51

Imagine a Star Wars type spaceship in orbit around a planet. Its engine suffers a severe malfunction, and explodes. What is the most physically realistic depiction of this event?

A) The spacecraft breaks in half, and begins to sink down into the planet, like a sinking aircraft carrier.
B) The spacecraft breaks apart, and the pieces continue to orbit the planet.
C) The spacecraft burns up in a giant fireball.

Question 52

As an interstellar cloud of hydrogen gas shrinks in size, its rate of rotation

A) increases, because its angular momentum is conserved.
B) decreases, because its angular momentum is conserved.
C) increases, because its total energy is conserved.
D) increases, because the force of gravity strengthens as the cloud shrinks.
E) decreases, because the force of gravity strengthens as the cloud shrinks.

Question 53

If a gas cloud shrinks, it

A) spins at the same rate as it did before it shrank.
B) spins faster.
C) spins slower.

Question 54

As an interstellar cloud of hydrogen gas shrinks in size, its temperature increases,

A) because gravitational potential energy is converted to thermal energy.
B) because kinetic energy is converted to radiative energy.
C) because thermal energy is converted to radiative energy.

Question 55

Consider the elliptical orbit of a comet around the Sun. Where in its orbit is the comet moving the fastest?

A) When it is farthest from the Sun
B) It is always moving at the same speed.
C) When it is closest to the Sun

Question 56

A popular end for many cartoon characters is to fall into a "bottomless pit" in which the unfortunate character will fall forever. Consider the space shuttle in orbit around the Earth. Argue that there is a strong analogy between the cartoon "bottomless pit" and the orbital motion of the shuttle.

Question 57

Explain what synchronous rotation is. What is it caused by? Give an example.

Question 58

How does a rocket launch upwards? Choose the statement that best describes why a rocket goes up.

A) By expelling gas downwards, the rocket is propelled upwards
B) Expelling gas downwards, which by pushing against the ground, propels the rocket upwards

Question 59

Suppose a satellite is in a low-Earth orbit. Is it possible that the satellite will eventually fall to the ground? Why or why not?

Question 60

The astronauts feel weightless in the International Space Station, which orbits the Earth once every 90 minutes. Why?

A) Because there is no gravity in space
B) Because they are moving so fast
C) Because the gravity from the Moon cancels out the gravity from Earth
D) Because they are falling around the Earth

Question 61

Radiative energy is ________.

A) energy carried by light
B) heat energy
C) energy from nuclear power plants
D) energy of motion

Question 62

If I drop a golf ball and a bowling ball simultaneously from same height above the ground, what will happen? Neglect the effects of wind or air resistance.

A) The golf ball and the bowling ball will hit the ground at the same time.
B) The bowling ball will hit the ground before the golf ball.
C) The golf ball will hit the ground before the bowling ball.

Question 63

What is the difference between a bound orbit and an unbound orbit around the Sun?

A) An object on a bound orbit follows the same path around the Sun over and over, while an object on an unbound orbit approaches the Sun just once and then never returns.
B) A bound orbit is an orbit allowed by the universal law of gravitation, and an unbound orbit is not.
C) An object on a bound orbit has a gravitational attraction to the Sun, while an object on an unbound orbit does not.
D) A bound orbit is circular, while an unbound orbit is elliptical.

Question 64

Suppose that two objects collide. Which of the following things is not the same both before and after the collision?

A) The total temperature of the objects
B) The total momentum of the objects
C) The total angular momentum of the objects
D) The total energy of the objects

Question 65

Momentum is defined as ________.

A) mass times velocity
B) mass times speed
C) force times velocity
D) mass times acceleration

Question 66

In which of the following cases would you feel weightless?

A) While falling from a roof
B) While parachuting from an airplane
C) While accelerating downward in an elevator
D) While walking on the Moon

Question 67

In the formula E=mc², what does E represent?

A) The mass-energy, or potential energy stored in an object's mass
B) The kinetic energy of a moving object
C) The radiative energy carried by light
D) The gravitational potential energy of an object held above the ground
E) The electric field produced by a charge

Question 68

Absolute zero is ________.

A) 0 Kelvin
B) 0∘ Celsius
C) 0∘ Fahrenheit
D) 100∘ Celsius

Question 69

What does temperature measure?

A) The average kinetic energy of particles in a substance
B) The average mass of particles in a substance
C) The total potential energy of particles in a substance
D) The total amount of heat in a substance

Question 70

Newton's Second Law of Motion tells us that the net force applied to an object equals its ________.

A) mass times acceleration
B) mass times energy
C) momentum times velocity
D) mass times velocity

Question 71

Why is Newton's version of Kepler's third law so useful to astronomers?

A) It can be used to determine the masses of many distant objects.
B) It allows us to calculate distances to distant objects.
C) It tells us that more-distant planets orbit the Sun more slowly.
D) It explains why objects spin faster when they shrink in size.

Question 72

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them ________.

A) decreases by a factor of 9
B) increases by a factor of 9
C) decreases by a factor of 3
D) increases by a factor of 3

Question 73

The acceleration of gravity on Earth is approximately 10 m/s² (more precisely, 9.8 m/s²). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

A) 30 m/s
B) 10 m/s
C) 30 m/s²
D) 10 m/s²
E) 20 m/s

Question 74

When a spinning ice skater pulls in his arms, he spins faster because ________.

A) his angular momentum must be conserved, so reducing his radius must increase his speed of rotation
B) there is less friction with the air
C) there is less friction with the ice
D) there exists an unbalanced reaction force

Question 75

What do we mean by the orbital energy of an orbiting object (such as a planet, moon, or satellite)?

A) Orbital energy is the sum of the object's kinetic energy and its gravitational potential energy as it moves through its orbit.
B) Orbital energy is the object's kinetic energy as it moves through its orbit.
C) Orbital energy is a measure of the object's speed as it moves through its orbit.
D) Orbital energy is the amount of energy required for the object to leave orbit and escape into space.

Question 76

The difference between speed and velocity is that ________.

A) they are expressed in different units
B) velocity also includes a direction
C) velocity is the same as acceleration but speed is different
D) velocity is calculated using a physics equation

Question 77

The gravitational force that the Earth exerts on the Moon is equal and opposite to that which the Moon exerts on the Earth. Therefore, according to Newton's second law of motion,

A) the Moon as a larger acceleration than the Earth, because it has a smaller mass.
B) the Moon and the Earth both have equal accelerations, because the forces are equal.
C) the Earth has a larger acceleration than the Moon, because it has a larger mass.

Question 78

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 acting upon it, an object moves with constant velocity.
D) For any force, there always is an equal and opposite reaction force.

Question 79

The energy attributed to an object by virtue of its motion is known as ________.

A) kinetic energy
B) potential energy
C) radiative energy
D) mass-energy

Question 80

Suppose you lived on the Moon. Which of the following would be true?

A) Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
B) Both your weight and your mass would be less than they are on Earth.
C) Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth.
D) Both your weight and your mass would be the same as they are on Earth.