Question 1

Einstein's theory of relativity is based in part on which one of the following postulates?
A)Mass and energy are equivalent.
B)Space and time are absolutes.
C)Energy is conserved only in elastic collisions.
D)Speed of light in a vacuum is same for all observers regardless of source velocity.

Accepted Answer

Einstein's theory of relativity is based in part on the postulate that the speed of light in a vacuum is the same for all observers regardless of the source's velocity. This postulate is often referred to as the constancy of the speed of light.

Question 2

The speed of light is equal to A)5.28 × 10⁷ miles per hour. B)one meter per nanosecond. C)one light-year per year. D)none of the above.

Accepted Answer

The speed of light is commonly expressed as one light-year per year, which means that light travels a distance of one light-year in one year. One light-year is the distance that light can travel in a vacuum in one year, which is approximately 5.88 trillion miles. Therefore, the answer is C, "one light-year per year." Choices A and B are incorrect as they provide incorrect units for the speed of light. Choice D is incorrect as one of the given options must be correct.

Question 3

A mass is bouncing on the end of a spring with a period T when measured by a ground observer.What would the period of oscillation be (as measured by the same observer)if the mass and spring were moving past the ground observer at a speed of 0.9c?
A)5.3 T
B)0.40 T
C)3.2 T
D)2.3 T
E)​1.1 T

Accepted Answer

D

Question 4

The experiment that dispelled the idea that light travels in the ether is called the
A)Michelson-Morley experiment.
B)Hafele and Keating experiment.
C)Fitzgerald-Kennedy experiment.
D)twin paradox.

Accepted Answer

The Michelson-Morley experiment was designed to measure the speed of the Earth's motion through the ether, but the results showed that there was no ether and that light travels at a constant speed in all directions. This helped to confirm Albert Einstein's theory of relativity and revolutionized our understanding of the nature of light and the universe. The Hafele and Keating experiment confirmed the effects of time dilation predicted by the theory of relativity, and the Fitzgerald-Kennedy experiment provided additional evidence for the absence of the ether, but neither of these experiments were directly related to the nature of light itself. The twin paradox is a thought experiment that explores the consequences of time dilation, but it does not directly address the properties of light.

Question 5

Doubling the momentum of
A)a particle doubles its relativistic total energy.
B)a particle quadruples its relativistic total energy.
C)a photon doubles its relativistic total energy.
D)a photon quadruples its relativistic total energy.

Accepted Answer

Doubling the momentum of a photon doubles its relativistic total energy because both the energy and momentum of a photon are directly proportional to its frequency (or inversely proportional to its wavelength). Therefore, if the momentum is doubled, the energy also doubles, following the relationship E = pc for photons, where E is energy, p is momentum, and c is the speed of light.

Question 6

Which characterizes the main result of the Michelson-Morley experiment?
A)verified the existence of ether
B)involved measuring the speed of sound from a moving source
C)detected no difference in the speed of light regardless of speed of the source relative to observer
D)was designed purposely to verify Einstein's theory of relativity

Accepted Answer

The Michelson-Morley experiment attempted to detect the existence of ether, a hypothetical medium through which light waves were thought to propagate. However, the experiment failed to detect any difference in the speed of light regardless of the orientation of the apparatus or the speed of the Earth's motion. This result contradicted the prevailing theory of ether and paved the way for Einstein's theory of relativity.

Question 7

I am stationary in a reference system but if my reference system is not an inertial reference system,then,relative to me,a system that is an inertial reference system must
A)remain at rest.
B)move with constant velocity.
C)be accelerating.
D)be none of the above.

Accepted Answer

If you are stationary in a non-inertial reference system, it means that your reference system is accelerating. Therefore, an inertial reference system, which is not accelerating, must appear to be accelerating relative to you.

Question 8

According to the special theory of relativity,if a 30-year old astronaut sent on a space mission is accelerated to speeds close to that of light,and then returns to Earth after 20 years as measured on Earth,what would be his biological age upon returning?
A)less than 50 years
B)50 years
C)more than 50 years
D)exactly 100 years

Accepted Answer

According to the special theory of relativity, time slows down for objects that are moving at high speeds. Therefore, when the astronaut travels at speeds close to that of light, time for him will appear to slow down relative to time on Earth. This means that although 20 years have passed on Earth, the astronaut's biological age would be less than 50 years upon returning due to time dilation.

Question 9

What is proper time?
A)Proper time is the time measured by a clock at rest with respect to the observer.
B)Proper time is time based on your actual longitude,not your time zone.
C)Proper time is the time given on your GPS.
D)Proper time means standard time as opposed to daylight savings time.

Accepted Answer

Proper time is the time measured by a clock that is stationary relative to the observer. It takes into account time dilation due to special relativity and can be different for observers in different reference frames.

Question 10

The observed relativistic length of a super rocket moving by the observer at 0.70c will be what factor times that of the measured rocket length if it were at rest?
A)0.55
B)0.71
C)0.51
D)1.4
E)​1.8

Accepted Answer

The observed relativistic length contraction can be calculated using the formula $L = L_0\sqrt{1 - v^2/c^2}$, where $L_0$ is the rest length, $v$ is the velocity of the object, and $c$ is the speed of light. Plugging in $v = 0.70c$, we get $L = L_0\sqrt{1 - 0.49} = L_0\sqrt{0.51}$, which is approximately $L = 0.71L_0$.

Question 11

According to the special theory of relativity,which of the following happens to the length of an object,measured in the dimension parallel to the motion of its inertial frame of reference,as the velocity of this frame increases with respect to a stationary observer?
A)length increases
B)length decreases
C)length remains constant
D)length vanishes to zero when velocity equals half speed of light

Accepted Answer

According to the special theory of relativity, as the speed of an object increases relative to a stationary observer, its length measured in the dimension parallel to the motion of the frame of reference decreases. This is known as length contraction. Therefore, the correct choice is B, which states that the length decreases. Option D is incorrect since length contraction does not cause an object's length to vanish to zero.

Question 12

The period of a pendulum is 1.5 s in a stationary inertial frame of reference.What is its period when measured by an observer moving at a speed of 0.75 c with respect to the inertial frame of reference?
A)1.0 s
B)3.4 s
C)2.3 s
D)3.0 s
E)​0.8 s

Accepted Answer

The period of the pendulum will appear longer to the moving observer due to time dilation, which is a consequence of special relativity. The formula for time dilation is T' = T / sqrt(1 - v^2/c^2). Substituting the given values, T' = 1.5 / sqrt(1 - (0.75)^2) = 2.3 s.

Question 13

That the speed of light in a vacuum has the same value for all inertial frames is
A)inconsistent with the results of the Michelson-Morley experiment.
B)consistent with the results of the Michelson-Morley experiment.
C)not related to the results of the Michelson-Morley experiment.
D)not true.

Accepted Answer

The Michelson-Morley experiment aimed to detect the presence of the hypothetical "ether," which was thought to be the medium through which light waves propagate. The experiment found no evidence of the ether, which was a surprise to the scientists of the time. However, it also showed that the speed of light was constant, regardless of the direction of the experiment or the speed of the observer. This result is consistent with the postulate of special relativity that the speed of light in a vacuum is constant for all inertial observers, regardless of their relative motion. Therefore, the statement that the speed of light in a vacuum has the same value for all inertial frames is consistent with the results of the Michelson-Morley experiment.

Question 14

Which statement regarding Einstein's theories is correct?​
A)​According to special relativity,moving clocks run more slowly than those at rest,and according to general relativity,clocks higher in a gravity field run more quickly..
B)​According to special relativity,moving clocks run more quickly than those at rest,and according to general relativity,clocks higher in a gravity field also run more quickly..
C)​According to special relativity,moving clocks run more quickly than those at rest,and according to general relativity,clocks higher in a gravity field run more slowly..
D)​According to special relativity,moving clocks run more quickly than those at rest,and according to general relativity,clocks higher in a gravity field also run more quickly.

Accepted Answer

Special relativity posits that moving clocks run slower compared to those at rest, a phenomenon known as time dilation. General relativity further states that clocks in a higher gravitational field (or further from a massive object) run faster than those in a stronger gravitational field.

Question 15

The Michelson-Morley experiment was designed to make use of ________ to find the motion of the Earth relative to the luminiferous ether.
A)sound waves
B)interference fringes
C)electromagnetic wind
D)none of the above

Accepted Answer

The Michelson-Morley experiment utilized interference fringes created by splitting and then recombining light beams to detect the Earth's motion through the supposed luminiferous ether, which was believed to be the medium for light waves.

Question 16

According to the special theory of relativity,which of the following happens to the size of the time interval between two events occurring in an inertial frame of reference as the frame's velocity with respect to the observer increases?
A)interval increases
B)interval decreases
C)interval remains constant
D)interval vanishes to zero when velocity equals half speed of light

Accepted Answer

According to the special theory of relativity, as the velocity of an inertial frame of reference increases with respect to an observer, the observed time interval between two events occurring in that frame (from the perspective of the observer) increases. This phenomenon is known as time dilation.

Question 17

A spaceship,which has length 35 m and width 16 m when at rest,is moving in a direction along its length at a speed where its length contraction results in a 28-m length measured by a stationary observer.What would the measured width be in this case?
A)between 18 and 20 m
B)16 m
C)13 m
D)less than 13 m
E)​20 m

Accepted Answer

Length contraction only affects the dimensions of an object in the direction of its motion. Since the width of the spaceship is perpendicular to its direction of motion, it remains unchanged at 16 m, as observed by a stationary observer.

Question 18

According to a postulate of Einstein,which of the following describes the nature of the laws of physics as one observes processes taking place in various inertial frames of reference?
A)Laws are same only in inertial frames with zero velocity.
B)Laws are same only in inertial frames moving at low velocities.
C)Laws are same only in inertial frames moving at near speed of light.
D)Laws are same in all inertial frames.

Accepted Answer

According to the special theory of relativity postulate, the laws of physics are the same in all inertial frames of reference, regardless of their velocities. This is known as the principle of relativity. Therefore, D is the correct choice.

Question 19

The relativistic effect of time dilation has been verified by which of the following?
A)the discovery of black holes
B)muon experiments
C)twin experiments
D)red shift in distant galaxies

Accepted Answer

Muon experiments have provided strong evidence for the time dilation effect predicted by relativity. Muons, subatomic particles with a very short half-life, are created in the upper atmosphere and should decay before reaching Earth's surface due to their short lifetime. However, they are observed to reach the surface, indicating that time appears to pass more slowly for them due to their high velocity. This is consistent with the time dilation effect predicted by relativity.

Question 20

The significant result of the Michelson-Morley experiment was that it found
A)the ether moved with the Sun.
B)the ether moved with the Earth.
C)the speed of the ether wind was greater than expected.
D)no effect.

Accepted Answer

The Michelson-Morley experiment found no effect, which meant that they did not detect any significant difference in the speed of light caused by the motion of the Earth through the hypothetical ether. This result challenged the prevailing belief in the existence of the ether and was a crucial step in the development of Einstein's theory of special relativity.

Quiz 26: Relativity

Einstein's theory of relativity is based in part on which one of the following postulates?

The speed of light is equal to

A mass is bouncing on the end of a spring with a period T when measured by a ground observer.What would the period of oscillation be (as measured by the same observer) if the mass and spring were moving past the ground observer at a speed of 0.9c?

The experiment that dispelled the idea that light travels in the ether is called the

Doubling the momentum of

Which characterizes the main result of the Michelson-Morley experiment?

I am stationary in a reference system but if my reference system is not an inertial reference system,then,relative to me,a system that is an inertial reference system must

According to the special theory of relativity,if a 30-year old astronaut sent on a space mission is accelerated to speeds close to that of light,and then returns to Earth after 20 years as measured on Earth,what would be his biological age upon returning?

What is proper time?

The observed relativistic length of a super rocket moving by the observer at 0.70c will be what factor times that of the measured rocket length if it were at rest?

According to the special theory of relativity,which of the following happens to the length of an object,measured in the dimension parallel to the motion of its inertial frame of reference,as the velocity of this frame increases with respect to a stationary observer?

The period of a pendulum is 1.5 s in a stationary inertial frame of reference.What is its period when measured by an observer moving at a speed of 0.75 c with respect to the inertial frame of reference?

That the speed of light in a vacuum has the same value for all inertial frames is

Which statement regarding Einstein's theories is correct?

The Michelson-Morley experiment was designed to make use of ________ to find the motion of the Earth relative to the luminiferous ether.

According to the special theory of relativity,which of the following happens to the size of the time interval between two events occurring in an inertial frame of reference as the frame's velocity with respect to the observer increases?

A spaceship,which has length 35 m and width 16 m when at rest,is moving in a direction along its length at a speed where its length contraction results in a 28-m length measured by a stationary observer.What would the measured width be in this case?

According to a postulate of Einstein,which of the following describes the nature of the laws of physics as one observes processes taking place in various inertial frames of reference?

The relativistic effect of time dilation has been verified by which of the following?

The significant result of the Michelson-Morley experiment was that it found