Question 1

Which statement below is true?

Accepted Answer

A) If we could build a spaceship capable of traveling at a speed very near the speed of light,passengers on the ship could make a journey to a star that is 500 light-years away within their lifetimes. 
B) If we could build a spaceship capable of traveling at a speed very near the speed of light,we could send a ship to a star that is 500 light-years away and it would return just a few years after we launched it. 
C) Thanks to effects of special relativity,we could build a spaceship that could go close to the speed of light with much less fuel than we would have guessed from Newton's laws of motion. 
D) Because special relativity tells us that we cannot reach or exceed the speed of light,it means that distant stars will never be within our reach because the time required to reach them will always be quite long,even with very fast spaceships. 
A) If we could build a spaceship capable of traveling at a speed very near the speed of light,passengers on the ship could make a journey to a star that is 500 light-years away within their lifetimes. 
B) If we could build a spaceship capable of traveling at a speed very near the speed of light,we could send a ship to a star that is 500 light-years away and it would return just a few years after we launched it. 
C) Thanks to effects of special relativity,we could build a spaceship that could go close to the speed of light with much less fuel than we would have guessed from Newton's laws of motion. 
D) Because special relativity tells us that we cannot reach or exceed the speed of light,it means that distant stars will never be within our reach because the time required to reach them will always be quite long,even with very fast spaceships. A

Question 2

You and Al are both floating freely in your spaceships.Suppose that Al is moving away from you at 85 km/hr.You throw a ball in his direction at a speed of 75 km/hr.According to Al,which of the following is going on?

Accepted Answer

A) He sees you moving toward him at 85 km/hr and the ball moving toward him at 75 km/hr. 
B) He sees you moving away from him at 85 km/hr and the ball moving toward him at 10 km/hr. 
C) He agrees that he is moving at 85 km/hr and the ball is moving at 75 km/hr while you are standing still. 
D) He sees you moving away from him at 85 km/hr and the ball moving away from him at 10 km/hr. 
A) He sees you moving toward him at 85 km/hr and the ball moving toward him at 75 km/hr. 
B) He sees you moving away from him at 85 km/hr and the ball moving toward him at 10 km/hr. 
C) He agrees that he is moving at 85 km/hr and the ball is moving at 75 km/hr while you are standing still. 
D) He sees you moving away from him at 85 km/hr and the ball moving away from him at 10 km/hr. D

Question 3

Scientists believe in the theory of relativity because it was invented by Einstein,even though very little experimental evidence supports it.

Accepted Answer

A) True 
 B)False  False

Question 4

Consider the same scenario as in the previous problem: Two twin sisters,Gwen and Jackie,are both 20 years old in the year 2020.Jackie takes off on a round-trip to Vega,25 light-years away.She travels at an average speed of 0.9999c.Which of the following best describes the situation according to Jackie?

Accepted Answer

A) She stays still,while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c.Since Vega is 25 light-years away,she says it takes Vega about 25 years to reach her. 
B) She says that the 25 light-year trip takes only a few months,and therefore concludes that she is traveling faster than the speed of light. 
C) It takes her 25 years to reach Vega. 
D) She stays still,while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c.She sees the distance from Earth to Vega shortened considerably from 25 light-years,and therefore it takes far less than 25 years for Vega to reach her. 
A) She stays still,while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c.Since Vega is 25 light-years away,she says it takes Vega about 25 years to reach her. 
B) She says that the 25 light-year trip takes only a few months,and therefore concludes that she is traveling faster than the speed of light. 
C) It takes her 25 years to reach Vega. 
D) She stays still,while Earth rushes away from her at 0.9999c and Vega rushes toward her at 0.9999c.She sees the distance from Earth to Vega shortened considerably from 25 light-years,and therefore it takes far less than 25 years for Vega to reach her.

Question 5

A super train is moving along a track at a speed close to the speed of light.You are watching the train from the ground.You observe lightning to strike in two places along the track,a mile apart,at precisely the same time.What would someone on the train say?

Accepted Answer

A) The two bolts of lightning struck at different times,and they struck at places that are more than a mile apart. 
B) The two bolts of lightning struck at the same time,and they struck at places that are less than a mile apart. 
C) The two bolts of lightning struck at different times,and they struck at places that are precisely a mile apart. 
D) The two bolts of lightning struck at different times,and they struck at places that are less than a mile apart. 
A) The two bolts of lightning struck at different times,and they struck at places that are more than a mile apart. 
B) The two bolts of lightning struck at the same time,and they struck at places that are less than a mile apart. 
C) The two bolts of lightning struck at different times,and they struck at places that are precisely a mile apart. 
D) The two bolts of lightning struck at different times,and they struck at places that are less than a mile apart.

Question 6

Which of the following statements best describes what is "relative" in the theory of relativity?

Accepted Answer

A) The theory says that everything is relative. 
B) The theory says that truth can never be established in any absolute sense. 
C) The theory says that measurements of motion make sense only when we state what they are measured relative to. 
D) The theory says that the speed of light is relative and depends on who is measuring it. 
E) The theory says that all scientific results must be considered within the context of the scientists' individual viewpoints. 
A) The theory says that everything is relative. 
B) The theory says that truth can never be established in any absolute sense. 
C) The theory says that measurements of motion make sense only when we state what they are measured relative to. 
D) The theory says that the speed of light is relative and depends on who is measuring it. 
E) The theory says that all scientific results must be considered within the context of the scientists' individual viewpoints.

Question 7

If you could measure the mass of a moving object,you would find that it was greater than its value when stationary.

Accepted Answer

A) True 
 B)False

Question 8

Suppose that,as you sit in your classroom,you see two balls fall to the floor and hit at exactly the same time.According to the theory of relativity,other people sitting in the classroom with you will not agree that the balls hit the floor at the same time.

Accepted Answer

A) True 
 B)False

Question 9

Each of the following lists two statements.Which two are the basic premises for the special theory of relativity?

Accepted Answer

A) 1.The laws of nature are the same for everyone. 2.The speed of light is the same for everyone. 
B) 1.Everything is relative. 2.You can never really tell who is moving. 
C) 1.You can't go faster than the speed of light. 2.Time is different for different people. 
D) 1.The laws of nature are the same for everyone. 2.Everything is relative. 
E) 1.The speed of light is the same for everyone. 2.You can't go faster than the speed of light. 
A) 1.The laws of nature are the same for everyone. 2.The speed of light is the same for everyone. 
B) 1.Everything is relative. 2.You can never really tell who is moving. 
C) 1.You can't go faster than the speed of light. 2.Time is different for different people. 
D) 1.The laws of nature are the same for everyone. 2.Everything is relative. 
E) 1.The speed of light is the same for everyone. 2.You can't go faster than the speed of light.

Question 10

A spaceship is headed toward Alpha Centauri at 0.999c.According to us,the distance to Alpha Centauri is about 4 light-years.How far away is Alpha Centauri according to the travelers in the ship?

Accepted Answer

A) also about 4 light-years 
B) very slightly more than 4 light-years 
C) very slightly less than 4 light-years 
D) quite a bit less than 4 light-years 
E) quite a bit more than 4 light-years 
A) also about 4 light-years 
B) very slightly more than 4 light-years 
C) very slightly less than 4 light-years 
D) quite a bit less than 4 light-years 
E) quite a bit more than 4 light-years

Question 11

The idea that the speed of light is absolute is supported by experimental evidence.

Accepted Answer

A) True 
 B)False

Question 12

According to the authors of the text,the theory of relativity

Accepted Answer

A) does not violate our common sense. 
B) violates common sense because it contradicts logic. 
C) violates common sense because it is counterintuitive. 
D) violates common sense because the theory contradicts itself in many cases. 
E) violates common sense because it is full of paradoxes. 
A) does not violate our common sense. 
B) violates common sense because it contradicts logic. 
C) violates common sense because it is counterintuitive. 
D) violates common sense because the theory contradicts itself in many cases. 
E) violates common sense because it is full of paradoxes.

Question 13

Carol is going away from you at 75 km/hr,and Sam is going in the opposite direction away from you at 90 km/hr.According to Carol,how fast is Sam going?

Accepted Answer

A) Carol sees Sam going away from her at 75 km/hr. 
B) Carol sees Sam going away from her at 90 km/hr. 
C) Carol sees Sam going away from her at 15 km/hr. 
D) Carol sees Sam going away from her at 165 km/hr. 
E) Carol sees Sam coming toward her at 15 km/hr. 
A) Carol sees Sam going away from her at 75 km/hr. 
B) Carol sees Sam going away from her at 90 km/hr. 
C) Carol sees Sam going away from her at 15 km/hr. 
D) Carol sees Sam going away from her at 165 km/hr. 
E) Carol sees Sam coming toward her at 15 km/hr.

Question 14

Why do the predicted consequences of the special theory of relativity seem so strange to most of us?

Accepted Answer

A) because they are self-contradictory,making it impossible to make any sense of them 
B) because they are obvious only at speeds that we never experience in our daily lives 
C) because they contradict the well-tested ideas of Newton's laws of motion 
D) because they affect only subatomic particles and not big things like people 
A) because they are self-contradictory,making it impossible to make any sense of them 
B) because they are obvious only at speeds that we never experience in our daily lives 
C) because they contradict the well-tested ideas of Newton's laws of motion 
D) because they affect only subatomic particles and not big things like people

Question 15

The primary difference between the special theory of relativity and the general theory of relativity is that the general theory also describes

Accepted Answer

A) length contraction. 
B) the nature of gravity. 
C) time dilation. 
D) the constancy of the speed of light. 
A) length contraction. 
B) the nature of gravity. 
C) time dilation. 
D) the constancy of the speed of light.

Question 16

According to the theory of relativity,the speed of light is absolute (meaning that everyone always measures it to have the same value).

Accepted Answer

A) True 
 B)False

Question 17

Two twin sisters,Gwen and Jackie,are both 20 years old in the year 2020.Jackie takes off on a round-trip to Vega,25 light-years away.She travels at an average speed very close to the speed of light-say,0.9999c.According to Gwen back on Earth,about how long does it take Jackie to reach Vega?

Accepted Answer

A) about a month 
B) about 10 years 
C) about 25 years 
D) about 100 years 
A) about a month 
B) about 10 years 
C) about 25 years 
D) about 100 years

Question 18

If we could measure the mass of the spaceship as it goes by,what would it be?

Accepted Answer

A) Its mass is infinite. 
B) Its mass is greater than its rest mass. 
C) Its mass is the same as it would be if it were not moving. 
D) Its mass is less than its rest mass. 
A) Its mass is infinite. 
B) Its mass is greater than its rest mass. 
C) Its mass is the same as it would be if it were not moving. 
D) Its mass is less than its rest mass.

Question 19

Suppose you stay home on Earth while your twin sister takes a trip to a distant star and back in a spaceship that travels at 99 percent of the speed of light.If both of you are 25 years old when she leaves and you are 45 years old when she returns,how old is your sister when she gets back?
Hint: Recall that the time dilation formula is:
 $ t^{\prime}=\sqrt[t]{1-\left(\frac{v}{c}\right)^{2}} $ 
where t is the time according to the person at home and is the time for the traveler.

Accepted Answer

Your sister's speed is v = 0.99c,or v/c

Question 20

The lifetime of a Π⁺ meson normally is 18 nanoseconds.In a large particle accelerator,scientists can create p+ mesons moving at speeds very close to the speed of light.What do the scientists observe when they measure the lifetime of a Π⁺ meson that is created at very high speed?

Accepted Answer

A) The Π⁺ meson lasts 18 nanoseconds. 
B) The Π⁺ meson lasts much less than 18 nanoseconds. 
C) The Π⁺ meson lasts much more than 18 nanoseconds. 
D) The Π⁺ meson no longer decays,and remains as a stable particle. 
A) The Π⁺ meson lasts 18 nanoseconds. 
B) The Π⁺ meson lasts much less than 18 nanoseconds. 
C) The Π⁺ meson lasts much more than 18 nanoseconds. 
D) The Π⁺ meson no longer decays,and remains as a stable particle.

Exam 26: Space and Time

Which statement below is true?

You and Al are both floating freely in your spaceships.Suppose that Al is moving away from you at 85 km/hr.You throw a ball in his direction at a speed of 75 km/hr.According to Al,which of the following is going on?

Scientists believe in the theory of relativity because it was invented by Einstein,even though very little experimental evidence supports it.

A super train is moving along a track at a speed close to the speed of light.You are watching the train from the ground.You observe lightning to strike in two places along the track,a mile apart,at precisely the same time.What would someone on the train say?

Which of the following statements best describes what is "relative" in the theory of relativity?

If you could measure the mass of a moving object,you would find that it was greater than its value when stationary.

Suppose that,as you sit in your classroom,you see two balls fall to the floor and hit at exactly the same time.According to the theory of relativity,other people sitting in the classroom with you will not agree that the balls hit the floor at the same time.

Each of the following lists two statements.Which two are the basic premises for the special theory of relativity?

A spaceship is headed toward Alpha Centauri at 0.999c.According to us,the distance to Alpha Centauri is about 4 light-years.How far away is Alpha Centauri according to the travelers in the ship?

The idea that the speed of light is absolute is supported by experimental evidence.

According to the authors of the text,the theory of relativity

Carol is going away from you at 75 km/hr,and Sam is going in the opposite direction away from you at 90 km/hr.According to Carol,how fast is Sam going?

Why do the predicted consequences of the special theory of relativity seem so strange to most of us?

The primary difference between the special theory of relativity and the general theory of relativity is that the general theory also describes

According to the theory of relativity,the speed of light is absolute (meaning that everyone always measures it to have the same value).

Two twin sisters,Gwen and Jackie,are both 20 years old in the year 2020.Jackie takes off on a round-trip to Vega,25 light-years away.She travels at an average speed very close to the speed of light-say,0.9999c.According to Gwen back on Earth,about how long does it take Jackie to reach Vega?

If we could measure the mass of the spaceship as it goes by,what would it be?

The lifetime of a Π⁺ meson normally is 18 nanoseconds.In a large particle accelerator,scientists can create p+ mesons moving at speeds very close to the speed of light.What do the scientists observe when they measure the lifetime of a Π⁺ meson that is created at very high speed?

A Modern View of the Universe

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Galaxies and the Foundations of Modern Cosmology

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