Deck 35: Special Theory of Relativity

Question 1

Einstein rejected the classical idea that space and time are

A)two parts of a whole.
B)connected to each other.
C)independent of each other.

Answer 1

independent of each other.

Question 2

The ether theory of light propagation is

A)much used.
B)incomplete, but still useful.
C)unexplained.
D)discredited.

Answer 2

discredited.

Question 3

The speed of light is

A)relative to the frame of reference from which it is measured.
B)a speed approached but never quite reached by photons.
C)constant for all observers.

Answer 3

constant for all observers.

Question 4

Compared to clocks in a stationary reference frame, clocks in a moving reference frame run

A)slower.
B)faster.
C)at the same rate.

Question 5

When you run along the hall from one classroom to another you're moving through

A)space.
B)time.
C)both of these
D)none of these

Question 6

Event A occurs before event B in a certain frame of reference. In another frame of reference, event A could occur

A)after event B.
B)simultaneous with event B.
C)either of these
D)neither of these

Question 7

To the surprise of Michelson and Morley, their interferometer experiment provided evidence that the speed of light is

A)invariant.
B)the same whether its source approaches or recedes.
C)constant.
D)all of the above

Question 8

According to Einstein, events that are simultaneous in one frame of reference

A)are simultaneous in all frames of reference.
B)are not simultaneous in other frames of reference.
C)may or may not be simultaneous in other frames of reference.

Question 9

The Lorentz factor, γ,

A)is always greater than 1 for any speed greater than zero.
B)lets the time-dilation equation be expressed t = γ t₀.
C)both of these
D)none of these

Question 10

What is special about the ratio distance traveled per unit of time?

A)it is constant for light
B)it is relative to a frame of reference
C)distance traveled very much depends on time

Question 11

The place from which motion is observed and measured is called

A)a frame of reference.
B)a starting point.
C)an initial location.

Question 12

Clocks on a spaceship moving at high speed relative to the Earth run more slowly when viewed from

A)within the spaceship.
B)Earth.
C)both of these
D)neither of these

Question 13

All events and all things exist in "the spacetime continuum" with coordinates

A)of distances in three dimensions.
B)of time.
C)both of these
D)none of these

Question 14

You and a friend can share the same space and time measurements when

A)you are side by side at rest.
B)you both are side by side moving at constant velocity.
C)either of these
D)none of these

Question 15

How fast would a light beam appear to Einstein if he were traveling in the same direction at 90% of the speed of light?

A)0
B)c
C)0.1c
D)1.10c
E)none of the above

Question 16

According to the special theory of relativity, all laws of nature are the same

A)in all reference frames.
B)for both linear or circular motion.
C)in all uniformly moving reference frames.
D)all of the above
E)none of the above

Question 17

The stretching out of time due to motion is called time

A)stretching.
B)dilation.
C)contraction.
D)warp.
E)expansion.

Question 18

An observer moving with a light clock in a spaceship sees a light flash bouncing up and down between parallel mirrors in 1 nanosecond. An observer at rest outside the spaceship sees the same up-and-down flash in

A)1 nanosecond also.
B)less than 1 nanosecond.
C)more than 1 nanosecond.

Question 19

A postulate of special relativity is that the speed of light

A)like all motion, is relative.
B)for all observers is a constant.
C)both of these
D)neither of these

Question 20

Two lightning bolts are seen to strike two distant locations at the same time. Seen from a different location, the two lightning bolts

A)will also be seen at the same time.
B)will not be seen at the same time.
C)may or may not be seen at the same time.

Question 21

As you approach a steady light source, the wavelength of the emitted light appears

A)longer.
B)shorter.
C)the same.

Question 22

Two spaceships approaching each other move at very close to the speed of light, each sending a beam of light to the other. Each measures the speed of light from the other spaceship as

A)slightly less than c.
B)c.
C)slightly greater than c.
D)much greater than c.

Question 23

If the frequency of blinks for a light source appears to double as the light source approaches you, the frequency of blinks as it moves away from you at the same speed

A)is halved.
B)is doubled.
C)stays the same.

Question 24

According to relativity theory, if a space trip finds a son or daughter biologically older than their parents, then the space trip is taken by the

A)son or daughter.
B)parents.
C)either of these
D)neither, it can't be done.

Question 25

According to the special theory of relativity, while traveling at very high speed your pulse rate

A)increases.
B)decreases.
C)remains unchanged.

Question 26

The clock on the Big Ben Tower in London reads 12 noon. If you travel away from the clock at a very high speed and view it with a telescope, you would see

A)run slower than a clock in your vehicle.
B)run faster than a clock in your vehicle.
C)be frozen at 12 noon.

Question 27

When a moving spaceship emits regularly-spaced flashes of light, how frequently you see the flashes depends on the ship

A)approaching you.
B)receding from you.
C)either of these
D)none of these

Question 28

As you recede from a steady light source, the wavelength of the emitted light appears

A)longer.
B)shorter.
C)the same.

Question 29

We are actually looking into the past when we look at

A)a distant star.
B)our physics book.
C)actually both of these
D)none of the above

Question 30

A light source blinks with a certain frequency in its own frame of reference, and the speed of light in that frame is c. When the light source approaches you, you observe an increase in

A)both speed of light and frequency of blinking.
B)speed of light, but not frequency of blinking.
C)frequency of blinking, but not speed of light.

Question 31

As a blinking light source uniformly accelerates away from you, you observe the blinks

A)more and more frequently.
B)less and less frequently.
C)neither of these

Question 32

A spaceship traveling very fast relative to you fires a stream of photons at speed c away from you. You measure the photons' speed to be

A)less than c.
B)more than c.
C)equal to c.

Question 33

Using the relativistic velocity-addition formula for adding everyday velocities produces

A)nonsense.
B)a significantly better result than adding them classically.
C)a classical result.

Question 34

When a blinking light source moves relative to you, the speed of the light

A)changes but the frequency of blinks remains constant.
B)remains constant but the frequency of blinks can change.
C)stays the same, as does the blinking frequency.

Question 35

You look at the clock on the Big Ben Tower in London and it reads 12 noon. If you could hypothetically travel away from the clock at the speed of light and view it with a telescope, it would

A)run slower than a clock in your vehicle.
B)run faster than a clock in your vehicle.
C)be frozen at 12 noon.

Question 36

As a light source blinking at a steady rate approaches you at an increasing speed (accelerating toward you), the rate at which the blinks encounter you

A)increases.
B)decreases.
C)remains the same.

Question 37

Harry takes a space voyage and returns to find his twin sister has aged more than he has. This is evidence that

A)she has changed frames of reference.
B)he has changed frames of reference.
C)both have changed frames of reference.
D)neither has changed frames of reference

Question 38

A certain light source blinks once per second in its own frame of reference. As you recede from the blinking source, you observe the frequency of blinks to be

A)less than 1 Hz.
B)1 Hz.
C)more than 1 Hz.

Question 39

Suppose you and your sister travel at different speeds in space and you note a slowing of her clock. Compared with her clock your sister will notice that your clock runs

A)faster.
B)slower.
C)the same.
D)need more information

Question 40

A light source blinks once per second in its own frame of reference. As you approach the blinking source, you observe the frequency of blinks to be

A)less than 1 Hz.
B)1 Hz.
C)more than 1 Hz.

Question 41

The length of a 100-meter long spaceship passing by you at 0.87c is seen to be

A)50 m.
B)87 m.
C)100 m.
D)125 m.
E)150 m.

Question 42

When an object of mass m is pushed to relativistic speed v, its momentum is

A)greater than mv.
B)smaller than mv.
C)equal to mv.

Question 43

As the speed of a particle approaches the speed of light, the momentum of the particle

A)approaches zero.
B)approaches infinity.
C)transforms to energy.
D)is no longer in spacetime.

Question 44

An astronaut traveling forward at 0.87c holds a meterstick in spear-like fashion. This astronaut sees the spear's length as

A)0.5 m.
B)0.87 m.
C)1 m.
D)1.25 m.
E)1.5 m.

Question 45

An astronaut traveling forward at 0.87c holds a meterstick in spear-like fashion. An observer at rest sees the spear's length as

A)0.5 m.
B)0.87 m.
C)1 m.
D)1.25 m.
E)1.5 m.

Question 46

According to special relativity, tomorrow's travelers can travel

A)only forward in time.
B)backward in time.
C)both forward and backward in time.

Question 47

When a high-velocity beam of electrons is bent by a magnetic field, relativistic effects

A)increase momentum beyond its classical value.
B)reduce the angle at which the beam is bent.
C)both of these
D)neither of these

Question 48

A 10-meter-long spear is thrown at relativistic speeds through a 10-meter-long pipe. (Both these dimensions are measured when each is at rest.)When the spear passes through the pipe

A)the spear appears to shrink so the pipe completely covers it.
B)the pipe appears to shrink so the spear extends from both ends.
C)both appear to shrink equally so the pipe barely covers the spear.
D)any of these, depending on the motion of the observer (moving with the spear, at rest with the pipe, and so on).
E)none of the above

Question 49

There is an upper limit on the speed of a particle, which means there is also an upper limit on its

A)momentum.
B)kinetic energy.
C)both of these
D)neither of these

Question 50

To outside observers at rest, the overall sizes of objects traveling at relativistic speeds are

A)larger.
B)smaller.
C)the same size.

Question 51

As a spaceship moves away from you at half the speed of light, it fires a probe, also away from you at half the speed of light relative to the spaceship. Relative to you, the probe moves at

A)0.80c.
B)0.87c.
C)0.90c.
D)0.95c.
E)c.

Question 52

As a spaceship moving toward you at half the speed of light fires a probe toward you, relative to itself at 0.7 the speed of light, you see the probe approaching at about

A)0.70c.
B)0.87c.
C)0.89c.
D)0.92c.
E)0.96c.

Question 53

Relative to some reference frame in the universe, you may now be traveling at a speed

A)faster than the speed of light.
B)slower than the speed of light.
C)at the speed of light.
D)any of the above

Question 54

Radioactive muons formed high in the atmosphere have an average lifetime of 2 millionths of a second and travel toward Earth at nearly the speed of light. Because of their altitude most of them should have decayed by the time they reach the Earth's surface, according to pre-relativity physics. They don't because they

A)live longer due to time dilation.
B)travel a shorter distance due to length contraction.
C)both of these
D)neither of these

Question 55

A spaceship whizzes past a planet at high speed. An observer on the planet sees a contracted spaceship, while an observer on the spaceship sees

A)a contracted planet.
B)an expanded planet.
C)a normal planet.
D)a contracted or expanded planet depending on the direction of travel.

Question 56

When we apply the Lorentz factor γ to momentum, we

A)multiply by γ as with the equation for time dilation.
B)multiply by the reciprocal of γ.
C)find it does not apply.

Question 57

A girl standing on the ground observes a rocket ship move past her at half the speed of light. Compared to the rocket's length at rest, she sees the rocket's length as

A)longer.
B)shorter.
C)the same length.

Question 58

When we apply the Lorentz factor γ to length contraction, we

A)multiply by γ as in the equation for time dilation.
B)multiply by the reciprocal of γ
C)find it does not apply.

Question 59

A heavy meterstick has mass m. When the meterstick is thrown like a spear past you at speed v, you measure its momentum to be 2mv. What do you measure its length to be?

A)1 m
B)0.87 m
C)0.5 m
D)0.25 m
E)none of the above

Question 60

Objects moving at relativistic speeds appear to observers at rest to be

A)stretched.
B)shrunken.
C)either depending on direction of motion.
D)none of the above

Question 61

If an antimatter meteor of mass m were to strike the Earth, the amount of radiant energy produced would be

A)less than mc².
B)mc².
C)2mc².
D)none of the above

Question 62

According to the well-known equation E = mc²,

A)mass and energy travel at the speed of light squared.
B)energy is actually mass traveling at the speed of light squared.
C)mass and energy travel at twice the speed of light.
D)mass and energy are related.
E)none of the above

Question 63

When an electron and a positron meet and annihilate, the mass-energy of the particles is carried away by

A)a gamma ray.
B)two gamma rays, otherwise momentum wouldn't be conserved.
C)nothing at all, gone.

Question 64

What does c² have in common with γ?

A)they are both proportionality constants
B)they have similar numerical values
C)they both involve different kinds of speed
D)all of the above

Question 65

Electrons fired in vintage TV tubes traveled at about 0.25 times the speed of light, having more momentum and energy than would be required classically to get that speed. Strictly speaking, this

A)increased your electric bill.
B)decreased your electric bill.
C)had no effect on your electric bill.

Question 66

According to Einstein's theory of special relativity

A)space and time are aspects of each other.
B)energy and mass are aspects of each other.
C)both of these
D)neither of these

Question 67

When you shake an apple to and fro, you're shaking

A)energy.
B)nothing.
C)the universe.

Question 68

Relativity equations for time, length and momentum hold true for

A)relativistic speeds.
B)everyday low speeds.
C)both of these
D)neither of these