Deck 10: The Special Theory of Relativity

Question 1

One experimental observation that demonstrates Einstein's ideas on the relativity of time, is

A) electromagnetic waves from the early stages of the development of the universe have slower rates of vibration.
B) rapidly- rotating neutron stars spin more slowly than they would if they weren't moving rapidly away from us.
C) muons "live" longer when moving rapidly than they do when they are at rest.
D) a laser beam emitted from an orbiting satellite is observed from Earth.
E) the recent discovery of very fast- moving particles known as tachyons.

Answer 1

muons "live" longer when moving rapidly than they do when they are at rest.

Question 2

Can a rock be accelerated up to lightspeed?

A) No, because any material object's length decreases to zero as the object approaches lightspeed.
B) No, because the theory of relativity states that it is impossible for anything to move at lightspeed.
C) No, because any material object's mass becomes infinite as the object approaches lightspeed.
D) Yes, as we can see from the example of light itself.
E) Yes, by projecting the object at a sufficiently high speed from a reference frame that is already moving at a high speed.

Answer 2

No, because any material object's mass becomes infinite as the object approaches lightspeed.

Question 3

Before Einstein, scientists thought that the substance that was "waving" when a light wave was transmitted was

A) plasma.
B) ether.
C) air.
D) phlogisten.
E) They didn't think any material substance was waving.

Answer 3

ether.

Question 4

Nineteenth- century scientists thought the "ether" to be

A) the medium for the propagation of sound waves.
B) the cause of the gravitational force.
C) the medium for the propagation of light waves.
D) All of the above.
E) None of the above.

Question 5

Velma passes Mort at a high speed. According to Mort, his clock has progressed by one hour while Velma's clock progressed by only 40 minutes. What does Velma observe?

A) Mort's clock progressed by one hour while Velma's clock progressed by 80 minutes.
B) Mort's clock progressed by one hour while Velma's progressed by 40 minutes.
C) Mort's clock progressed by 40 minutes while Velma's clock progressed by one hour.
D) both clocks progressed by one hour.
E) The answer cannot be determined, because we don't know Velma's speed.

Question 6

In Einstein's special theory of relativity, there is one basic principle [or assumption, or law] that seems very odd to our intuitions, and that is responsible for the odd nature of Einstein's conclusions. This basic principle is

A) the idea that mass is relative, and is larger when it is moved faster.
B) the idea that all motion is merely relative motion, i.e., that it is impossible to determine how fast you are moving without measuring against something outside your laboratory.
C) the idea that light has the same speed for all nonaccelerated observers.
D) E = mc².
E) relativistic length contraction.

Question 7

According to Einstein's theory of relativity, how much energy is contained in the material of a one kilogram rock that is at rest on the ground?

A) None at all.
B) 9 × 10¹⁰ joules
C) 3 × 10¹⁶ joules
D) 10^{- 16} joules
E) 9 × 10¹⁶ joules

Question 8

Velma passes Mort at a speed of 0.75c. At this speed, the "time dilation factor" is 1.5. In other words, Mort observes a 1- second tick of Velma's clock to take 1.5 seconds. Suppose that they are born at the same time, and that Velma observes herself to live 30 years. According to Mort's observations, how old is he when Velma dies?

A) 30 years
B) 45 years
C) 20 years
D) 10 years
E) 40 years

Question 9

Mort's twin, Velma, flies to a distant star at high speed and returns to Mort on Earth. She then finds that

A) she has been changed into a giraffe.
B) she is younger than Mort.
C) Mort is younger than her.
D) they are the same age.
E) they are both younger than each other.

Question 10

Velma is in a rocket ship moving north past Mort at half of lightspeed relative to Mort. She fires a laser beam forward from the front of her ship. Mort sees the laser beam move at

A) c.
B) 0.5c.
C) slightly faster than c.
D) 1.5c.
E) slightly slower than speed c [lightspeed].

Question 11

The graph above shows the relativity of time, space, and mass [you will need to figure out which graph goes with which effect]. How fast would Velma have to fly across Chicago in order to observe the city's width to be reduced 10% below the width measured on the ground?

A) about 99% of lightspeed
B) about 90% of lightspeed
C) about 45% of lightspeed
D) about 1.01c
E) Nonsense-- if Velma is flying across Chicago, she will observe the city's width to be larger than normal.

Question 12

A certain star is 1000 light years from Earth. According to the theory of relativity, is it physically possible for Mort to travel from Earth to this star during Mort's normal lifetime?

A) No, because Mort cannot travel faster than light.
B) No, because the relativity of time will cause Mort to age too rapidly.
C) No, because Mort's aging process is normal as measured in their own reference frame.
D) Yes, by traveling at nearly lightspeed.
E) Yes, by traveling much faster than lightspeed.

Question 13

According to Einstein's theory,

A) material objects get easier to accelerate as they move faster.
B) material objects become less massive as they go faster and faster.
C) no material object can be accelerated up to lightspeed.
D) nothing can move at lightspeed.
E) there are no limitations on the speed of any object.

Question 14

Which of the following is a form of radiation and not a form of matter?

A) carbon dioxide gas
B) the electron beam that creates the picture on a TV tube
C) an electric current flowing in a copper wire
D) None of the above are forms of radiation.
E) All of the above are forms of radiation.

Question 15

Using the graph above, how fast must Velma move past Mort if he is to observe her spaceship's length to be reduced by 50%?

A) about 25% of lightspeed
B) about 85% of lightspeed
C) 70% of lightspeed
D) 50% of lightspeed
E) about 95% of lightspeed

Question 16

The two great theories of 20th- century physics are

A) thermodynamics and electromagnetism.
B) high energy physics and the theory of relativity.
C) electromagnetism and the theory of relativity.
D) quantum theory and electromagnetism.
E) the theory of relativity and quantum theory.

Question 17

The two major physical theories of the 20th century are

A) electromagnetic theory and the theory of gravity.
B) superconductivity and the theory of light.
C) electromagnetic theory and quantum theory.
D) quantum theory and the theory of relativity.
E) the theory of relativity and electromagnetic theory.

Question 18

The two great theories of 20th- century physics are quantum theory and

A) electromagnetism.
B) Hamiltonian mechanics.
C) thermodynamics.
D) the theory of relativity.
E) the bootstrap theory of elementary particles.

Question 19

According to the theory of relativity, is everything relative?

A) No, time and space are not relative.
B) No, velocity is not relative.
C) No, lightspeed is not relative.
D) Yes.
E) No, mass is not relative.

Question 20

You separate two magnets that are initially held together by magnetic forces. How does this affect the mass and energy of the system of magnets?

A) It creates additional mass, located within each magnet, and also additional energy.
B) It creates additional energy, located in the space between the two magnets, but not additional mass.
C) It creates additional mass, located within each magnet, but no additional energy.
D) It creates neither additional energy nor additional mass.
E) It creates additional mass, located in the space between the two magnets, and also additional energy.

Question 21

Velma, who is carrying a "light clock," passes Mort at a high speed. Velma observes that, during one tick of her own light clock, the light beam on her clock travels

A) no distance at all.
B) further than 300,000 km.
C) 300,000 km.
D) a distance of one light year.
E) less than 300,000 km.

Question 22

Alphonse moves eastward in a car at 30 m/s. Velma, moving eastward in a train at 70 m/s, passes him. Alphonse's velocity relative to Velma is

A) 100 m/s eastward.
B) 30 m/s westward.
C) 40 m/s eastward.
D) 40 m/s westward.
E) 100 m/s westward.

Question 23

According to Einstein's mass- energy relation,

A) a stretched rubber band has slightly greater mass than the same rubber band when unstretched.
B) a heated object has slightly greater mass than the same object when it was cooler.
C) Both of the above.
D) None of the above.

Question 24

According to Einstein's theory of relativity, the universe is made of

A) matter and anti- matter.
B) popcorn.
C) energy.
D) radiation.
E) matter.

Question 25

Velma is in a train moving north at 20 m/s. She throws a stone toward the rear of the train, at 5 m/s relative to herself. Mort, standing beside the tracks, sees the stone move

A) south at 15 m/s.
B) north at 20 m/s.
C) south at 25 m/s.
D) north at 25 m/s.
E) north at 15 m/s.

Question 26

Material objects cannot be accelerated up to lightspeed because

A) of the curvature of space, which increases toward infinite curvature as the object approaches lightspeed.
B) their length decreases [toward zero] as they approach lightspeed.
C) their inertia increases [toward infinity, i.e., without bound] as they approach lightspeed.
D) nothing can move at the speed of light.
E) Nonsense-- objects can be sped up to lightspeed, as we can see from the example of light itself.

Question 27

Which of the following is one way of stating the principle of relativity?

A) No physical experiment, conducted entirely within your own lab, can tell you how fast you are moving relative to anything outside the lab.
B) The speed of light is relative to the motion of the observer, provided that the observer is not accelerated.
C) Light has the same speed for all nonaccelerated observers, regardless of the motion of the source or observer.
D) Experiments conducted entirely within your own lab will come out differently, depending on the state of motion of the lab relative to other reference frames.
E) Observers that are accelerated will see light beams move at something other than lightspeed.

Question 28

You lift a 1 kilogram object [weight on Earth = 10 N] by 1 meter. How much does the object's energy increase?

A) 10 watts
B) 1 watt
C) 1 joule
D) 10 joules
E) Its energy doesn't change at all.

Question 29

Mort stands on Earth. Velma moves away from him in a rocket at 299,000 km/s (1000 km/s slower than lightspeed). Mort sends a laser beam toward Velma. As the tip of the beam passes her rocket, Mort observes the beam to move just 1000 km/s faster than Velma, while Velma observes the beam to move at 300,000 km/s. Whose observation is correct?

A) Mort's
B) Velma's
C) both
D) neither

Question 30

The graph above shows the relativity of space. Suppose that Velma is riding in a spaceship that is 100 m long and 10 m high as measured by Velma. Roughly how fast must she be moving past Mort in order for Mort to measure her spaceship's length to be 50 meters?

A) about 0.8c
B) about 0.4c
C) about 0.87c
D) about 0.92c
E) Mort will not observe her spaceship's length to be 50 meters, no matter how fast she moves.

Question 31

Mort and Velma are twins, born at the same time on Earth. Velma is taken on a long trip into outer space, at a speed close to lightspeed, and returns to Earth. When she returns,

A) Mort observes that he is older than Velma, and Velma observes that she is older than Mort.
B) Mort observes that he is younger than Velma, but Velma will observe that she is younger than Mort.
C) Mort and Velma both observe that Mort is older than Velma.
D) Mort and Velma observe that they have aged equally.
E) Mort and Velma both observe that Velma is older than Mort.

Question 32

Velma is in a train moving eastward at 70 m/s. She throws a ball toward the rear of the train, throwing it at her normal "throwing speed" of 20 m/s. The ball's velocity relative to Mort, who is standing beside the tracks, is

A) 50 m/s westward.
B) 90 m/s eastward.
C) 20 m/s eastward.
D) 20 m/s westward.
E) 50 m/s eastward.

Question 33

Mort observes Velma's light- clock, as Velma passes. He observes that, during a 1 second tick of her clock, her light beam travels

A) a distance of one light year.
B) further than 300,000 km.
C) 300,000 km.
D) less than 300,000 km.
E) no distance at all.

Question 34

Suppose you are inside a smooth- flying [no bumps] jet plane moving at constant speed in a straight line across the Atlantic Ocean. Can you detect this motion [i.e., can you tell that you are moving] without directly or indirectly making use of anything outside of your own reference frame? If so, how could you detect this; and if not, why not?

A) Yes. For example, if you dropped a coin you would find that it lands to the rear of the drop point.
B) Yes. For example, if you dropped a coin you would find that it lands to the front of the drop point.
C) No, because jet planes move far too slowly for such an effect to actually be observed.
D) No, because of the principle of the constancy of lightspeed.
E) No, because of the principle of relativity.

Question 35

Mort is on Earth, and Velma passes him at a high speed. Mort and Velma each carry a standard kilogram. Concerning the kilograms, Velma observes that

A) Velma's is less massive than 1 kilogram and Mort's has a mass of 1 kilogram.
B) Velma's has a mass of 1 kilogram, but Mort's is more massive than 1 kilogram.
C) Velma's has a mass of 1 kilogram, but Mort's is less massive than 1 kilogram.
D) Velma's is more massive than 1 kilogram and Mort's has a mass of 1 kilogram.
E) both have a mass of 1 kilogram.

Question 36

A conclusion that follows from E=mc² is that, at the microscopic level,

A) there is only matter and antimatter.
B) all matter must vibrate at the speed of light.
C) tiny indestructible pieces of matter move through empty space.
D) matter is made of force fields.
E) matter is made of radiation.

Question 37

Velma bicycles northward at an unchanging speed of 4 m/s, and Mort jogs southward at an unchanging speed of 4 m/s. Mort's velocity relative to Velma is

A) 8 m/s northward.
B) 4 m/s northward.
C) 8 m/s southward.
D) 4 m/s southward.
E) zero.

Question 38

Velma and Mort pass each other, in rocket ships, at a relative velocity of half of lightspeed. Velma has an ice cream cone which will melt in 5 minutes if not refrigerated. She removes her cone from the refrigerator, and allows it to melt. According to Mort, how long does it take for Velma's cone to melt?

A) less than 5 minutes
B) more than 5 minutes
C) 5 minutes
D) It could be either more than 5 minutes, or 5 minutes, depending on which observer is at rest.
E) It is impossible to answer this question, because such measurements of moving objects have no precise meaning.

Question 39

If you drop a coin inside a car that is turning a corner to the right, the coin will land

A) to the right of the drop point.
B) in North Dakota.
C) to the rear of the drop point.
D) to the left of the drop point.
E) right under the drop point.

Question 40

Has there ever been a situation in which a given quantity of matter was turned completely into non- material forms of energy?

A) Yes, in electron- positron pair production.
B) Yes, in all three of the above types of experiments.
C) Yes, in nuclear fission and fusion.
D) Yes, in electron- positron annihilation.
E) No, there must always be some matter left over.

Question 41

Which of these happens when one kilogram of uranium undergoes nuclear fission?

A) Heat and other forms of energy are created, but no matter is actually lost (or destroyed) in the process.
B) An unmeasurably small amount of matter is converted to other forms of energy.
C) About one percent of the matter is converted to other forms of energy.
D) About one percent of the matter disappears, but no other forms of energy are created.
E) All the uranium is converted to other forms of energy.

Question 42

Velma, who is moving past you at a high rate of speed, holds a meter stick and a standard kilogram. Is it possible that your measurements could show the standard kilogram to have a mass of 2 kg while the meter stick still has its normal length of 1 m?

A) Yes, if Velma holds the meter stick perpendicular to its direction of motion.
B) Yes, if Velma holds the meter stick parallel to its direction of motion.
C) No, because mass actually decreases with velocity, rather than increasing.
D) No; if the kilogram's mass has increased to 2 kg, then it must be longer than 1 m.
E) No; if the kilogram's mass has increased to 2 kg, then it must be shorter than 1 m.

Question 43

You are inside a jet plane moving at a constant velocity. You toss a rock straight up in the air, and then you keep your hand at the point of release. The rock comes down in your hand. This example illustrates

A) that moving clocks go slow.
B) the principle of relativity.
C) the principle of the constancy of lightspeed.
D) that light is a wave.
E) the Michelson- Morley experiment.

Question 44

The two great theories of 20th- century physics are the theory of relativity and

A) Hamiltonian mechanics.
B) thermodynamics.
C) electromagnetism.
D) quantum theory.
E) the bootstrap theory of elementary particles.

Question 45

We proved, using Einstein's two basic principles, that if Velma is moving past Mort then Mort should observe Velma's clock to go slow. This behavior of Velma's clock occurs because, as observed by Mort,

A) the light beam in Velma's light- clock travels at slower than the normal lightspeed.
B) the light beam in her light- clock travels less than 300,000 km during one of Velma's ticks.
C) the light beam in Velma's light- clock travels at faster than the normal lightspeed.
D) the light beam in her light- clock travels further than 300,000 km during one of Velma's ticks.
E) Velma's light- clock shortens along its direction of motion.

Question 46

The post- Newtonian age began in 1900 when

A) Michelson declared the Newtonian age was over.
B) Einstein introduced the special theory of relativity.
C) Einstein introduced the general theory of relativity.
D) Maxwell introduced electromagnetic waves.
E) Max Planck introduced the quantum of energy.

Question 47

What does E = mc² say-- that all energy has mass, or that all mass has energy?

A) All energy has mass.
B) It says both of these.
C) It says neither of these.
D) All mass has energy.

Question 48

Velma passes Mort at a high speed. Each holds a meter stick, oriented perpendicular to the direction of relative motion. Mort observes that

A) his meter stick is 1 m long, and Velma's meter stick is less than 1 m long.
B) his meter stick and Velma's meter stick are both shorter than 1 m.
C) his meter stick is 1 m long, and Velma's meter stick is longer than 1 m.
D) his meter stick is longer than 1 m, and Velma's meter stick is 1 m long.
E) his meter stick and Velma's meter stick are both 1 m long.

Question 49

Velma is in a train moving eastward at 20 m/s. She throws a ball toward the rear of the train, throwing it at her normal "throwing speed" of 20 m/s. What is Mort's observation, regarding the ball?

A) It moves westward at 40 m/s.
B) It moves eastward at 40 m/s.
C) It moves westward at 20 m/s.
D) It falls straight down.
E) It moves eastward at the same speed of the train, just keeping up with the train.

Question 50

Velma and Mort pass each other, in rocket ships, at a relative velocity of half of lightspeed. Velma has an ice cream cone which will melt in 5 minutes if not refrigerated. She removes her cone from the refrigerator, and allows it to melt. According to Velma, how long does it take for her own cone to melt?

A) 5 minutes
B) more than 5 minutes
C) less than 5 minutes
D) It could be either more than 5 minutes, or 5 minutes, depending on which observer is at rest.

Question 51

The center of our galaxy is 30,000 light years away. Could a person possibly travel there in her own lifetime?

A) No, because a person cannot travel at lightspeed.
B) No, because the trip would take longer than 30,000 years, and nobody lives this long.
C) No, because time dilation applies only to clocks and not to biological phenomena such as a person's lifetime.
D) Yes, by traveling at nearly lightspeed, because of time dilation or the "relativity of time."
E) Yes, by traveling faster than lightspeed, because of time dilation or the "relativity of time."

Question 52

Velma is in a train headed north past Mort at 30 m/s. Velma has a slingshot that can shoot pebbles at 40 m/s. Velma shoots a pebble toward the rear of the train. Velma observes the pebble's velocity to be

A) 70 m/s south.
B) 10 m/s south.
C) 10 m/s north.
D) 40 m/s south.
E) 70 m/s north.

Question 53

Einstein believed that the principle of relativity should apply to Maxwell's theory of electromagnetism. Which basic principle or law did this lead Einstein to propose?

A) the relativity of time
B) length contraction
C) E=mc²
D) the law of inertia
E) the constancy of lightspeed

Question 54

Velma passes Mort at a high speed. Velma and Mort each have identical light- clocks. Mort and Velma both observe both clocks to "tick" simultaneously at 12 noon on both clocks. Mort observes that Velma's next tick occurs

A) before his own clock ticks.
B) at the same time as the tick on his clock.
C) only after the second drink.
D) after his own clock ticks.
E) before or after or at the same time as his own tick, depending on Velma's precise speed.

Question 55

A meter stick having a rest mass of 1 kg moves past you. Your measurements show it to have a mass of 2 kg and a length of 1 m. How is the stick oriented, as observed by you?

A) perpendicular to its direction of motion
B) parallel to its direction of motion
C) It is impossible to say anything about the orientation without further information.
D) Nonsense-- if the stick's mass has increased to 2 kg, then it must be longer than 1 m.

Question 56

Einstein proposed two basic principles or laws as the foundation of his special theory of relativity. One of these principles is intuitively plausible, while the other seems quite implausible or odd to our intuitions. The principle that is intuitively plausible is

A) the principle of the constancy of lightspeed.
B) E=mc².
C) the principle of relativity.
D) the principle of time dilation.
E) the principle of inertia.

Question 57

The graph above shows the relativity of space. Suppose that Velma observes Mort's automobile as she passes it at 60% of lightspeed. She passes lengthwise over the automobile. Mort's automobile is 4 meters long as measured by Mort. How long is it as measured by Velma?

A) 3.2 meters
B) 3.2c meters
C) 0.8c meters
D) 0.8 meter
E) 4 meters

Question 58

Very early in his thinking about relativity, Einstein asked himself what a person would observe if he or she kept up with a lightbeam. In answer to this question, the theory of relativity states that

A) the observer would suddenly undergo a sex change.
B) this is not a valid question because a person cannot move as fast as a lightbeam.
C) time would speed up without limit, and would pass at an "infinite" rate.
D) the light beam would stand still and so time would stand still.
E) the observer own would continue to observe the same laws of physics.

Question 59

According to Einstein's E=mc² and the "field view of reality,"

A) an atom's mass arises from the energy of its own fields.
B) atoms are entirely empty space-- containing only fields.
C) Both of the above.
D) atoms are mostly empty space, and consist of very tiny indestructible material particles that are attached to the atom by means of electromagnetic and other fields.
E) chocolate ice cream vanishes whenever you don't look at it.

Question 60

"Unless you look outside, you cannot tell how fast you are going." This is one way of stating

A) the principle of the constancy of lightspeed.
B) the principle of relativity.
C) the relativity of time.
D) the relativity of space.
E) Galileo's theory of relativity.

Question 61

The basic difference between the special and general theories of relativity is that

A) the first deals with electricity and the second with magnetism.
B) the first deals with nonaccelerated observers and the second deals with accelerated observers.
C) the first assumes that the observers are at rest and the second allows the observers to move.
D) the first deals only with accelerated observers and the second deals with nonaccelerated observers.
E) actually there is no important difference between them.

Question 62

Velma passes Mort at a high speed. Each holds a meter stick, oriented parallel to the direction of relative motion. Mort observes that

A) his meter stick is longer than 1 m, and Velma's meter stick is 1 m long.
B) his meter stick is 1 m long, and Velma's meter stick is longer than 1 m.
C) his meter stick and Velma's meter stick are both shorter than 1 m.
D) his meter stick is 1 m long, and Velma's meter stick is less than 1 m long.
E) his meter stick and Velma's meter stick are both 1 m long.

Question 63

In which of the following processes does the system's total mass change?

A) An automobile speeds up.
B) A rubber ball is squeezed.
C) The total mass changes in both of the above processes.
D) The total mass changed in neither of the above processes.

Question 64

What feature of Einstein's theory of relativity is demonstrated by the phenomenon of matter- antimatter annihilation?

A) the relativity of mass
B) E = mc²
C) the relativity of time
D) the constancy of lightspeed
E) that too much television will give you gas pains and make you froth at the mouth

Question 65

What was Einstein's main reason for proposing the principle of the constancy of lightspeed?

A) The Michelson- Morley experiment showed that every observer observes the same speed for any lightbeam.
B) He believed that conservation of energy should be obeyed in every nonaccelerated reference frame.
C) His own observations of such simple phenomena as reflection and refraction convinced him that light must have the same speed for all observers.
D) This principle followed from his conclusions regarding the relativity of time and space.
E) He believed that Maxwell's theory of electromagnetism should obey the principle of relativity.

Question 66

The meaning of the phrase "space is relative" is that

A) all observers measure the same speed for a lightbeam.
B) two observers, in different reference frames, observe different lengths for the same object.
C) two observers, both in the same reference frame, observe different lengths for different objects.
D) two observers, in different reference frames, observe different lengths for different objects.
E) two observers, both in the same reference frame, observe different lengths for the same object.

Question 67

Mort stands on Earth. Velma moves away from him in a rocket, at 299,000 km/s (1000 km/s slower than lightspeed). Mort sends a laser beam toward Velma. As the tip of the beam passes her rocket, Velma observes that

A) the laser beam moves past her at just 1000 km/s.
B) the laser beam moves past her at 300,000 km/s.
C) Both of the above.
D) the laser beam never catches up with her.
E) Mort has turned into a giant frog.

Question 68

Velma zooms past Mort at half of lightspeed. Velma observes Mort's clock to run

A) slow.
B) fast.
C) on time.
D) None of the above.

Question 69

Is it possible, according to Einstein's relativity, for a child to be biologically older than his or her parents?

A) Yes, if the parents go on a long and fast trip and return to Earth.
B) Yes, if the child goes on a long and fast trip and returns to Earth.
C) No, because it is not possible to actually move backward through time.
D) No, because the principles of relativity don't have anything to do with actual biological aging.
E) No, because the "relativity of time" does not allow the actual order of events in time to be switched around.

Question 70

Velma passes Mort at a high speed. Each holds a meter stick, oriented parallel to the direction of relative motion. Velma observes that

A) her meter stick is 1 m long, and Mort's meter stick is less than 1 m long.
B) her meter stick is 1 m long, and Mort's meter stick is longer than 1 m.
C) her meter stick and Mort's meter stick are both 1 m long.
D) her meter stick and Mort's meter stick are both shorter than 1 m.
E) her meter stick is longer than 1 m, and Mort's meter stick is 1 m long.

Question 71

Velma, inside a train moving at 20 m/s, throws a rock in the forward direction at 5 m/s. According to her the rock moves at 5 m/s. According to Mort, standing on Earth outside the train, the rock moves at [approximately] 25 m/s. Who is correct?

A) Mort, because he is standing on Earth.
B) The Wizard of Oz.
C) Neither, because there is no universal "best" reference frame.
D) Velma, because she threw the rock.
E) Both, relative to their own reference frames.

Question 72

One way of stating the principle of relativity is:

A) Experiments conducted entirely within your own lab will come out differently, depending on the state of motion of the lab relative to other reference frames.
B) Observers that are accelerated will see light beams move at something other than lightspeed.
C) Light has the same speed for all nonaccelerated observers.
D) Unless you look outside, you cannot tell how fast you are going.
E) The speed of light is relative to the motion of the observer, provided that the observer is not accelerated.

Question 73

In the "special theory of relativity," what does the word "special" refer to?

A) This theory is restricted to the study of gravitational forces.
B) This theory is restricted to the observations of stationary observers.
C) This theory is restricted to the observations of non- accelerated observers.
D) This theory is restricted to the study of light beams.
E) This theory is restricted to the observations of accelerated observers.

Question 74

You are inside a jet plane moving at a constant velocity. You toss a rock straight up in the air, and then you keep your hand at the point of release. The rock will come down

A) in your hand.
B) beside your hand.
C) behind your hand.
D) in front of your hand.
E) Actually the rock won't come down.

Question 75

In one experiment showing that faster- moving objects have larger masses,

A) high- velocity rifle bullets are fired at targets and their impact is measured.
B) microscopic particles are released from rest in a gravitational field, and their acceleration is measured.
C) observers move along beside high- velocity rifle bullets, in order to measure the masses of the bullets.
D) a microscopic balance- beam is used to measure the speeds of particles emitted during radioactive decay.
E) high- speed microscopic particles pass through electromagnetic fields, and the bending of their path is measured.

Question 76

You are in a spaceship moving past Earth at nearly lightspeed and you observe Mort, who is on Earth. You measure his mass, pulse rate, and size. How are they different from the values measured by Mort himself?

A) Mass has increased, pulse rate has speeded up, and size is reduced along the direction of motion.
B) Mass has decreased, pulse rate has slowed down, and size is reduced along the direction of motion.
C) Mass has decreased, pulse rate has speeded up, and size is reduced along the direction of motion.
D) They are unchanged, i.e., they are normal.
E) Mass has increased, pulse rate has slowed down, and size is reduced along the direction of motion.

Question 77

Einstein's Relativity seems to say that, if Mort and Velma are twins and Velma goes on a trip and then returns, Velma will then be younger than Mort and Mort will be younger than Velma. What is wrong with this reasoning?

A) The effects of the theory of relativity cancel out due to Velma's acceleration, so that they are both really the same age when they get back together.
B) The prediction about Velma's observation is not correct, because Velma is accelerated.
C) The prediction about Mort's observation is not correct, because Velma is accelerated.
D) What's wrong with this reasoning is that Albert Einstein was a fool and a hothead.
E) Nothing is wrong with it.

Question 78

Velma passes Mort at a high speed. Velma and Mort each have identical light- clocks. Mort and Velma both observe both clocks to "tick" simultaneously at 12 noon on both clocks. Velma observes that Mort's next tick occurs

A) after her own clock ticks.
B) before her own clock ticks.
C) only when the moon is full.
D) before or after or at the same time as her own tick, depending on Velma's precise speed relative to Mort.
E) at the same time as the tick on her clock.

Question 79

When one kilogram of uranium undergoes nuclear fission,

A) the total amount of rest- mass is conserved.
B) the total amount of energy is conserved.
C) Both of the above.
D) Neither of the above.

Question 80

If you drop a coin inside a car that is slowing down, the coin will land

A) in front of the drop point.
B) to the side of the drop point.
C) in St. Louis.
D) to the rear of the drop point.
E) right under the drop point.