Question 1

The total energy of a moving electron is $0.758 \mathrm { MeV }$ What is the speed of the electron in terms of c? The rest mass energy of an electron is 0.511 MeV.

Accepted Answer

A)  0.739 c 
B)  0.794 c 
C)  0.306 c 
D)  0.933 c 
A)  0.739 c 
B)  0.794 c 
C)  0.306 c 
D)  0.933 c A

Question 2

Astronaut Hans leaves Earth in a spaceship traveling at a speed of 0.280c relative to the observer Brian at rest on Earth. Hans is holding a pencil at an angle of 30° with the direction of travel, as seen by Hans. What angle does the pencil make with the direction of travel, as seen by Brian on Earth?

Accepted Answer

A)  29° 
B)  30° 
C)  31° 
D)  33° 
E)  90° 
A)  29° 
B)  30° 
C)  31° 
D)  33° 
E)  90° C

Question 3

How much mass is lost during a reaction in which 1.7 × 108 MeV of energy is released? (c = 3.0 × 108 m/s, 1 eV = 1.6 × 10-19 J)

Accepted Answer

A)  1.8 × 10-8 kg 
B)  5.7 × 10-9 kg 
C)  1.9 × 10-17 kg 
D)  3.0 × 10-22 kg 
A)  1.8 × 10-8 kg 
B)  5.7 × 10-9 kg 
C)  1.9 × 10-17 kg 
D)  3.0 × 10-22 kg D

Question 4

If the mass of a 1.0-kg book could be entirely converted into electrical energy, how many kW ∙ h of energy would that generate? (c = 3.0 × 108 m/s)

Accepted Answer

Question 5

According to the equation E = mc2, an object turns into energy when it reaches the speed of light.

Accepted Answer

A) True 
 B)False

Question 6

Two spaceships approach each other along a straight line at a constant relative velocity of 0.9880c as measured by the captain of one of the ships. An observer on Earth is able to measure the speed of only one of the ships as 0.9000c. From the point of view of the observer on Earth, what is the speed of the other ship in terms of the speed of light?

Accepted Answer

The answer of Two spaceships approach each other along a...

Question 7

A spaceship traveling at constant velocity passes by Earth and later passes by Mars. In which frame of reference is the amount of time separating these two events the proper time?

Accepted Answer

A)  the Earth frame of reference 
B)  the Mars frame of reference 
C)  the spaceship frame of reference 
D)  any inertial frame of reference 
E)  any frame of reference, inertial or not 
A)  the Earth frame of reference 
B)  the Mars frame of reference 
C)  the spaceship frame of reference 
D)  any inertial frame of reference 
E)  any frame of reference, inertial or not

Question 8

During a reaction, 170 µJ of energy is released. What change of mass would accompany this release? (c = 3.0 × 108 m/s)

Accepted Answer

A)  5.1 × 10-4 kg 
B)  1.5 × 10-13 kg 
C)  4.8 × 10-18 kg 
D)  1.9 × 10-21 kg 
A)  5.1 × 10-4 kg 
B)  1.5 × 10-13 kg 
C)  4.8 × 10-18 kg 
D)  1.9 × 10-21 kg

Question 9

One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on his spaceship. At the end of this trip, what are (a) his own age and (b) the age of his Earth-based twin brother?

Accepted Answer

A)  (a) 20 y (b) 30 y 
B)  (a) 30 y (b) 50 y 
C)  (a) 50 y (b) 70 y 
D)  (a) 70 y (b) 90 y 
A)  (a) 20 y (b) 30 y 
B)  (a) 30 y (b) 50 y 
C)  (a) 50 y (b) 70 y 
D)  (a) 70 y (b) 90 y

Question 10

Astronaut Jill leaves Earth in a spaceship and is now traveling at a speed of 0.280c relative to an observer on Earth. When Jill left Earth, the spaceship was equipped with all kinds of scientific instruments, including a meter stick. Now that Jill is underway, how long does she measure the meter stick to be?

Accepted Answer

A)  1.00 m 
B)  0.960 m 
C)  1.04 m 
D)  0.280 m 
E)  1.28 m 
A)  1.00 m 
B)  0.960 m 
C)  1.04 m 
D)  0.280 m 
E)  1.28 m

Question 11

An electron has a speed of 0.783c. Through what potential difference would the electron need to be accelerated from rest in order to reach this speed? The rest mass energy of an electron is 0.511 MeV.

Accepted Answer

A)  310 kV 
B)  260 kV 
C)  360 kV 
D)  400 kV 
A)  310 kV 
B)  260 kV 
C)  360 kV 
D)  400 kV

Question 12

You are riding in a spaceship that has no windows, radios, or other means for you to observe or measure what is outside. You wish to determine if the ship is stopped or moving at constant velocity. How can you do this?

Accepted Answer

A)  You can determine if the ship is moving by determining the apparent velocity of light in the spaceship. 
B)  You can determine if the ship is moving by checking your precision time piece. If it's running slow, the ship is moving. 
C)  You can determine if the ship is moving by lying down and measuring your height. If you are shorter than usual, the ship is moving. 
D)  You should give up because you have taken on an impossible task! 
A)  You can determine if the ship is moving by determining the apparent velocity of light in the spaceship. 
B)  You can determine if the ship is moving by checking your precision time piece. If it's running slow, the ship is moving. 
C)  You can determine if the ship is moving by lying down and measuring your height. If you are shorter than usual, the ship is moving. 
D)  You should give up because you have taken on an impossible task!

Question 13

Astronaut Sarah leaves Earth in a spaceship at a speed of 0.280c relative to Earth. Sarah's destination is a star system 12.5 light-years away (one light-year is the distance light travels in one year). According to Sarah, how far did she travel during the trip?

Accepted Answer

A)  13.0 light-years 
B)  12.5 light-years 
C)  12.0 light-years 
D)  11.5 light-years 
E)  11.0 light-years 
A)  13.0 light-years 
B)  12.5 light-years 
C)  12.0 light-years 
D)  11.5 light-years 
E)  11.0 light-years

Question 14

During a reaction, a reactant loses 4.8 × 10-28 kg of mass. How many joules of energy are released? (c = 3.0 × 108 m/s)

Accepted Answer

A)  4.3 × 10-11 J 
B)  1.4 × 10-19 J 
C)  1.6 × 10-36 J 
D)  5.3 × 10-45 J 
A)  4.3 × 10-11 J 
B)  1.4 × 10-19 J 
C)  1.6 × 10-36 J 
D)  5.3 × 10-45 J

Question 15

You are a passenger on a spaceship. As the speed of the spaceship increases, you will observe

Accepted Answer

A)  your watch slowing down. 
B)  your watch speeding up. 
C)  your watch losing time. 
D)  your watch gaining time. 
E)  nothing unusual about the behavior of your watch. 
A)  your watch slowing down. 
B)  your watch speeding up. 
C)  your watch losing time. 
D)  your watch gaining time. 
E)  nothing unusual about the behavior of your watch.

Question 16

A satellite with a rest mass of 200 kg and a speed of 0.800c and a second satellite with a rest mass of 100 kg and a speed of 0.600c are traveling toward each other in deep space. The satellites collide and somehow manage to stick together. What is the speed of the combined object after the collision?

Accepted Answer

A)  0.333c 
B)  0.374c 
C)  0.397c 
D)  0.418c 
E)  0.432c 
A)  0.333c 
B)  0.374c 
C)  0.397c 
D)  0.418c 
E)  0.432c

Question 17

The energy released by a certain reaction is enough to totally evaporate 125 kg of water at its boiling point. How much mass was lost during this reaction? (LF = 334,000 J/kg for water, c = 3.00 × 108 m/s)

Accepted Answer

Question 18

A certain unstable particle has a mean lifetime of 1.52 × 10-6 s. This is the time interval between its creation in a nuclear process and its extinction into decay products, as measured in a frame of reference at rest with respect to the particle. An average such particle is observed by a scientist on Earth to travel 342 m in its lifetime. What is the speed of the particle relative to Earth? (c = 3.00 × 108 m/s)

Accepted Answer

A)  0.821c 
B)  0.681c 
C)  0.600c 
D)  0.551c 
E)  0.335c 
A)  0.821c 
B)  0.681c 
C)  0.600c 
D)  0.551c 
E)  0.335c

Question 19

A particle in a 799=m-long linear particle accelerator is moving at $0.875 c$ How long does the particle accelerator appear to the particle?

Accepted Answer

A)  387 m 
B)  1039 m 
C)  184 m 
D)  1651 m 
A)  387 m 
B)  1039 m 
C)  184 m 
D)  1651 m

Question 20

One of Einstein's postulates in formulating the special theory of relativity was that the laws of physics are the same in reference frames that

Accepted Answer

A)  accelerate. 
B)  move at constant velocity with respect to an inertial frame. 
C)  oscillate. 
D)  are stationary, but not in moving frames. 
A)  accelerate. 
B)  move at constant velocity with respect to an inertial frame. 
C)  oscillate. 
D)  are stationary, but not in moving frames.

Exam 27: Relativity

The total energy of a moving electron is 0.758MeV0.758 \mathrm { MeV }0.758MeV What is the speed of the electron in terms of c? The rest mass energy of an electron is 0.511 MeV.

How much mass is lost during a reaction in which 1.7 × 108 MeV of energy is released? (c = 3.0 × 108 m/s, 1 eV = 1.6 × 10-19 J)

If the mass of a 1.0-kg book could be entirely converted into electrical energy, how many kW ∙ h of energy would that generate? (c = 3.0 × 108 m/s)

According to the equation E = mc2, an object turns into energy when it reaches the speed of light.

A spaceship traveling at constant velocity passes by Earth and later passes by Mars. In which frame of reference is the amount of time separating these two events the proper time?

During a reaction, 170 µJ of energy is released. What change of mass would accompany this release? (c = 3.0 × 108 m/s)

One 20-year-old twin brother takes a space trip with a speed of 0.80c for 30 years according to a clock on his spaceship. At the end of this trip, what are (a) his own age and (b) the age of his Earth-based twin brother?

An electron has a speed of 0.783c. Through what potential difference would the electron need to be accelerated from rest in order to reach this speed? The rest mass energy of an electron is 0.511 MeV.

You are riding in a spaceship that has no windows, radios, or other means for you to observe or measure what is outside. You wish to determine if the ship is stopped or moving at constant velocity. How can you do this?

Astronaut Sarah leaves Earth in a spaceship at a speed of 0.280c relative to Earth. Sarah's destination is a star system 12.5 light-years away (one light-year is the distance light travels in one year). According to Sarah, how far did she travel during the trip?

During a reaction, a reactant loses 4.8 × 10-28 kg of mass. How many joules of energy are released? (c = 3.0 × 108 m/s)

You are a passenger on a spaceship. As the speed of the spaceship increases, you will observe

The energy released by a certain reaction is enough to totally evaporate 125 kg of water at its boiling point. How much mass was lost during this reaction? (LF = 334,000 J/kg for water, c = 3.00 × 108 m/s)

A particle in a 799=m-long linear particle accelerator is moving at 0.875c0.875 c0.875c How long does the particle accelerator appear to the particle?

One of Einstein's postulates in formulating the special theory of relativity was that the laws of physics are the same in reference frames that

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The total energy of a moving electron is $0.758 \mathrm { MeV }$ What is the speed of the electron in terms of c? The rest mass energy of an electron is 0.511 MeV.

How much mass is lost during a reaction in which 1.7 × 10⁸ MeV of energy is released? (c = 3.0 × 10⁸ m/s, 1 eV = 1.6 × 10^-19 J)

If the mass of a 1.0-kg book could be entirely converted into electrical energy, how many kW ∙ h of energy would that generate? (c = 3.0 × 10⁸ m/s)

According to the equation E = mc², an object turns into energy when it reaches the speed of light.

During a reaction, 170 µJ of energy is released. What change of mass would accompany this release? (c = 3.0 × 10⁸ m/s)

During a reaction, a reactant loses 4.8 × 10^-28 kg of mass. How many joules of energy are released? (c = 3.0 × 10⁸ m/s)

The energy released by a certain reaction is enough to totally evaporate 125 kg of water at its boiling point. How much mass was lost during this reaction? (L_F = 334,000 J/kg for water, c = 3.00 × 10⁸ m/s)

A particle in a 799=m-long linear particle accelerator is moving at $0.875 c$ How long does the particle accelerator appear to the particle?