Question 1

The speed of light is equal to:

Accepted Answer

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

Question 2

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?

Accepted Answer

A)  1.0 s 
B)  3.4 s 
C)  2.3 s 
D)  3.0 s 
E)  ​0.8 s 
A)  1.0 s 
B)  3.4 s 
C)  2.3 s 
D)  3.0 s 
E)  ​0.8 s

Question 3

If astronauts could travel at v = 0.95 c,we on Earth would say it takes (4.2/0.95)= 4.4 years to reach Alpha Centauri,4.2 lightyears away.The astronauts disagree.How much time passes on the astronaut's clocks?

Accepted Answer

A)  1.4 years 
B)  14.1 years 
C)  4.0 years 
D)  1.3 years 
E)  ​0.4 years 
A)  1.4 years 
B)  14.1 years 
C)  4.0 years 
D)  1.3 years 
E)  ​0.4 years

Question 4

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

Accepted Answer

A)  the discovery of black holes 
B)  muon experiments 
C)  twin experiments 
D)  red shift in distant galaxies 
A)  the discovery of black holes 
B)  muon experiments 
C)  twin experiments 
D)  red shift in distant galaxies

Question 5

Through what potential difference would an electron initially at rest need to be accelerated to have its total energy be five times its rest energy? (me = 9.11 × 10-31 kg,c = 3.00 × 108 m/s,and qe = 1.6 × 10−19 C)

Accepted Answer

A)  1.6E-19 V 
B)  2.6E+6 V 
C)  2.0E+6 V 
D)  210 V 
E)  ​6.8E-3 V 
A)  1.6E-19 V 
B)  2.6E+6 V 
C)  2.0E+6 V 
D)  210 V 
E)  ​6.8E-3 V

Question 6

From a stationary position,I observe a moving boxcar,which has a mirror along the front wall,but it is open at the back of the boxcar.I send a flash of light from my flashlight and time the flash of light as it goes to the front of the boxcar and returns to the back of the boxcar.A passenger in the boxcar also times the round trip of the flash of light.Compare the times recorded on our watches.

Accepted Answer

A)  The time recorded on his watch is longer. 
B)  The time recorded on the two watches is the same. 
C)  The time recorded on his watch is shorter. 
D)  The answer depends on the reference system you are in. 
A)  The time recorded on his watch is longer. 
B)  The time recorded on the two watches is the same. 
C)  The time recorded on his watch is shorter. 
D)  The answer depends on the reference system you are in.

Question 7

In an x-ray tube,high-speed electrons are slammed into a lead target,giving off x-rays.If the electrons are accelerated from rest through a potential difference of 160 000 volts,what speed do they have when they strike the target? (qe = 1.6 × 10−19 C,me = 9.11 × 10−31 kg,and c = 3.00 × 108 m/s)

Accepted Answer

A)  0.79 c 
B)  0.65 c 
C)  0.83 c 
D)  0.49 c 
E)  ​0.48 c 
A)  0.79 c 
B)  0.65 c 
C)  0.83 c 
D)  0.49 c 
E)  ​0.48 c

Question 8

A spaceship of triangular shape,having a length three its width,is capable of relativistic speeds.How fast would it have to move so that to a stationary observer its length would equal its width?

Accepted Answer

A)  0.333 c 
B)  0.816 c 
C)  0.943 c 
D)  ​0.650 c 
E)  ​This is not possible. 
A)  0.333 c 
B)  0.816 c 
C)  0.943 c 
D)  ​0.650 c 
E)  ​This is not possible.

Question 9

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?

Accepted Answer

A)  length increases 
B)  length decreases 
C)  length remains constant 
D)  length vanishes to zero when velocity equals half speed of light 
A)  length increases 
B)  length decreases 
C)  length remains constant 
D)  length vanishes to zero when velocity equals half speed of light

Question 10

When one compares the relativistic kinetic energy to the classically calculated kinetic energy for a moving object,at which of the speeds listed below does the classical calculation give a greater value than the relativistic calculation?

Accepted Answer

A)  0.2 c 
B)  0.5 c 
C)  0.707 c 
D)  None of the above values will give such a result. 
A)  0.2 c 
B)  0.5 c 
C)  0.707 c 
D)  None of the above values will give such a result.

Question 11

The short lifetime of muons created in the upper atmosphere of the Earth would not allow them to reach the surface of the Earth unless their lifetime increased by time dilation.From the reference system of the muons,the muons can reach the surface of the Earth because:

Accepted Answer

A)  time dilation increases their velocity. 
B)  time dilation increases their energy. 
C)  length contraction decreases the distance to the Earth. 
D)  the relativistic speed of the Earth toward them is added to their velocity. 
A)  time dilation increases their velocity. 
B)  time dilation increases their energy. 
C)  length contraction decreases the distance to the Earth. 
D)  the relativistic speed of the Earth toward them is added to their velocity.

Question 12

A meter stick moving in a direction parallel to its length appears to be only 43.6 cm long to an observer.What is the meter stick's speed relative to the observer? (c = 3.00 × 108 m/s)

Accepted Answer

A)  2.25 × 108 m/s 
B)  1.69 × 108 m/s 
C)  2.70 × 108 m/s 
D)  1.31 × 108 m/s 
E)  ​2.95 × 108 m/s 
A)  2.25 × 108 m/s 
B)  1.69 × 108 m/s 
C)  2.70 × 108 m/s 
D)  1.31 × 108 m/s 
E)  ​2.95 × 108 m/s

Question 13

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

Accepted Answer

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 
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

Question 14

A muon formed high in Earth's atmosphere travels at a speed 0.960 c for a distance (as we see it)of 4500 m before it decays.How far does the muon travel as measured in its frame?

Accepted Answer

A)  2520 m 
B)  16,100 m 
C)  4320 m 
D)  1260 m 
E)  ​4500 m 
A)  2520 m 
B)  16,100 m 
C)  4320 m 
D)  1260 m 
E)  ​4500 m

Question 15

The gravitational field is equivalent to:

Accepted Answer

A)  the inertial mass. 
B)  an accelerated frame of reference. 
C)  an event horizon. 
D)  a clock running slowly. 
A)  the inertial mass. 
B)  an accelerated frame of reference. 
C)  an event horizon. 
D)  a clock running slowly.

Question 16

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 0.9 c?

Accepted Answer

A)  5.3 T 
B)  0.40 T 
C)  3.2 T 
D)  2.3 T 
E)  ​1.1 T 
A)  5.3 T 
B)  0.40 T 
C)  3.2 T 
D)  2.3 T 
E)  ​1.1 T

Question 17

A nuclear reaction,which gives off a total of 1.2 × 1017 J of energy,expends how much mass in the process? (c = 3.00 × 108 m/s)

Accepted Answer

A)  0.1 kg 
B)  1.3 kg 
C)  4.0 kg 
D)  13.3 kg 
E)  ​7.5 kg 
A)  0.1 kg 
B)  1.3 kg 
C)  4.0 kg 
D)  13.3 kg 
E)  ​7.5 kg

Question 18

A rocket ship is 87.0 m in length when measured before leaving the launching pad.What would its velocity be if a ground observer measured its length as 62.0 m while it is in flight? (c = 3.00 × 108 m/s)

Accepted Answer

A)  1.61 × 108 m/s 
B)  2.14 × 108 m/s 
C)  1.48 × 108 m/s 
D)  2.10 × 108 m/s 
E)  ​1.91 × 108 m/s 
A)  1.61 × 108 m/s 
B)  2.14 × 108 m/s 
C)  1.48 × 108 m/s 
D)  2.10 × 108 m/s 
E)  ​1.91 × 108 m/s

Question 19

A muon formed high in the Earth's atmosphere travels at a speed 0.870 c for a distance of 4.00 km before it decays.What is the muon's lifetime as measured in its reference frame?

Accepted Answer

A)  3.1E-5 s 
B)  7.6E-6 s 
C)  1.5E-5 s 
D)  5.1E-5 s 
E)  ​4.3E-5 s 
A)  3.1E-5 s 
B)  7.6E-6 s 
C)  1.5E-5 s 
D)  5.1E-5 s 
E)  ​4.3E-5 s

Question 20

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

Accepted Answer

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. 
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.

Exam 26: Relativity

The speed of light is equal to:

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?

If astronauts could travel at v = 0.95 c,we on Earth would say it takes (4.2/0.95)= 4.4 years to reach Alpha Centauri,4.2 lightyears away.The astronauts disagree.How much time passes on the astronaut's clocks?

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

Through what potential difference would an electron initially at rest need to be accelerated to have its total energy be five times its rest energy? (me = 9.11 × 10-31 kg,c = 3.00 × 108 m/s,and qe = 1.6 × 10−19 C)

A spaceship of triangular shape,having a length three its width,is capable of relativistic speeds.How fast would it have to move so that to a stationary observer its length would equal its width?

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?

When one compares the relativistic kinetic energy to the classically calculated kinetic energy for a moving object,at which of the speeds listed below does the classical calculation give a greater value than the relativistic calculation?

The short lifetime of muons created in the upper atmosphere of the Earth would not allow them to reach the surface of the Earth unless their lifetime increased by time dilation.From the reference system of the muons,the muons can reach the surface of the Earth because:

A meter stick moving in a direction parallel to its length appears to be only 43.6 cm long to an observer.What is the meter stick's speed relative to the observer? (c = 3.00 × 108 m/s)

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

A muon formed high in Earth's atmosphere travels at a speed 0.960 c for a distance (as we see it)of 4500 m before it decays.How far does the muon travel as measured in its frame?

The gravitational field is equivalent 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 0.9 c?

A nuclear reaction,which gives off a total of 1.2 × 1017 J of energy,expends how much mass in the process? (c = 3.00 × 108 m/s)

A rocket ship is 87.0 m in length when measured before leaving the launching pad.What would its velocity be if a ground observer measured its length as 62.0 m while it is in flight? (c = 3.00 × 108 m/s)

A muon formed high in the Earth's atmosphere travels at a speed 0.870 c for a distance of 4.00 km before it decays.What is the muon's lifetime as measured in its reference frame?

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

Introduction

Introduction: Part A

Motion in One Dimension

Motion in One Dimension: Part A

Vectors and Two-Dimensional Motion

Vectors and Two-Dimensional Motion: Part A

The Laws of Motion

The Laws of Motion: Part A

Energy

Energy: Part A

Momentum and Collisions

Momentum and Collisions: Part A

Rotational Motion and the Law of Gravity

Rotational Motion and the Law of Gravity: Part A

Rotational Equilibrium and Rotational Dynamics

Rotational Equilibrium and Rotational Dynamics: Part A

Solids and Fluids

Solids and Fluids: Part A

Thermal Physics

Thermal Physics: Part A

Energy in Thermal Processes Heat and Internal Energy

Energy in Thermal Processes Heat and Internal Energy: Part A

The Laws of Thermodynamics Work in Thermodynamic Processes

The Laws of Thermodynamics Work in Thermodynamic Processes: Part A

Vibrations and Waves

Vibrations and Waves: Part A

Sound

Sound: Part A

Electric Forces and Electric Fields

Electric Forces and Electric Fields: Part A

Electrical Energy and Capacitance

Electrical Energy and Capacitance: Part A

Current and Resistance Electric Current

Current and Resistance Electric Current: Part A

Direct-Current Circuits Sources of EMF

Direct-Current Circuits Sources of EMF: Part A

Magnetism Magnets

Magnetism Magnets: Part A

Induced Voltages and Inductance

Induced Voltages and Inductance: Part A

Alternating-Current Circuits and Electromagnetic Waves

Alternating-Current Circuits and Electromagnetic Waves: Part A

Reflection and Refraction of Light

Reflection and Refraction of Light: Part A

Mirrors and Lenses

Mirrors and Lenses: Part A

Wave Optics

Wave Optics: Part A

Optical Instruments

Optical Instruments: Part A

Relativity: Part A

Quantum Physics Blackbody Radiation and Plancks Hypothesis

Quantum Physics Blackbody Radiation and Plancks Hypothesis: Part A

Atomic Physics

Atomic Physics: Part A

Nuclear Physics

Nuclear Physics: Part A

Nuclear Energy and Elementary Particles

Nuclear Energy and Elementary Particles: Part A

Particle Collisions, Mediating Photons, and Quark Structures: Exploring the Fundamentals of Physics

Filters

Through what potential difference would an electron initially at rest need to be accelerated to have its total energy be five times its rest energy? (m_e = 9.11 × 10^-31 kg,c = 3.00 × 10⁸ m/s,and q_e = 1.6 × 10−¹⁹ C)

A meter stick moving in a direction parallel to its length appears to be only 43.6 cm long to an observer.What is the meter stick's speed relative to the observer? (c = 3.00 × 10⁸ m/s)

A nuclear reaction,which gives off a total of 1.2 × 10¹⁷ J of energy,expends how much mass in the process? (c = 3.00 × 10⁸ m/s)

A rocket ship is 87.0 m in length when measured before leaving the launching pad.What would its velocity be if a ground observer measured its length as 62.0 m while it is in flight? (c = 3.00 × 10⁸ m/s)