Question 1

Describe at least three pieces of evidence supporting the special theory of relativity.

Accepted Answer

The answer of Describe at least three pieces of evidence...

Question 2

Explain why relativity allows us to travel,in principle,to the center of the Milky Way,but we would never be able to tell our friends back home about it.

Accepted Answer

The answer of Explain why relativity allows us to travel,in...

Question 3

A spaceship is moving past you at a speed very close to the speed of light.If you could somehow watch the people inside it over a long period of time,what would you conclude?

Accepted Answer

A) They are aging more rapidly than you. 
B) Their mechanical clocks go slower than yours,but the people are aging at the same rate as you. 
C) Their time is the same as your time. 
D) They are aging more slowly than you.

Question 4

The general theory of relativity deals with the effects of gravity,but the special theory of relativity does not take gravity into account.

Accepted Answer

A) True 
 B)False

Question 5

A man is moving by you at a speed close to the speed of light.Which of the following correctly summarizes the effects you would notice on his mass,size,and time?

Accepted Answer

A) His mass would be increased from its value at rest,his length would be decreased from its rest value but only in the direction in which he is moving,and his time would be running slower than yours. 
B) His mass would be increased from its value at rest,his length,width,and height would all be decreased no matter what direction he is moving,and his time would be running slower than yours. 
C) His mass would be decreased from its value at rest,his length would be decreased from its rest value but only in the direction in which he is moving,and his time would be running slower than yours. 
D) His mass would be increased from its value at rest,his size would be increased,and his time would be running slower than yours.

Question 6

If you see Al going to your left at exactly 0.99c and Bob going to your right at exactly 0.99c,Al will say that Bob is

Accepted Answer

A) going away from her at 1.98c. 
B) going away from her at exactly 0.99c. 
C) going away from her at exactly c. 
D) going away from her at about 0.98c. 
E) going away from her faster than 0.99c,but slower than c.

Question 7

Ben is racing a light beam in a 100-meter dash.Ben bursts out of the starting blocks at 99 percent of the speed of light (0.99c).At the same instant,a flashlight beam is turned on from the starting blocks.
-Refer to the race described above.According to the spectators watching in the stands,what happens?

Accepted Answer

A) The light beam wins the race,but barely-it is going 1 percent of the speed of light faster than Ben. 
B) The light beam instantly finishes the race,before Ben even has a chance to start. 
C) The light beam wins the race by a large margin because it is going faster than Ben by the full speed of light. 
D) Ben beats the light beam to the finish line,becoming a hero.

Question 8

In what way do observations of binary star systems support the special theory of relativity?

Accepted Answer

A) Stars in binary systems often orbit at speeds close to the speed of light,allowing us to check whether time dilation really occurs. 
B) Stars in binary systems are moving,so we can compare their moving masses to their rest masses. 
C) The fact that the stars appear distinct supports the idea that the speed of light is unaffected by the motion of the stars. 
D) Binary systems have two stars,and therefore give us twice the opportunity to test the theory than single star systems.

Question 9

The fact that we cannot travel faster than the speed of light means that it is theoretically impossible for us to make trips to distant stars within our lifetimes.

Accepted Answer

A) True 
 B)False

Question 10

Again consider the scenario from the previous problem: A sprinter named Ben has challenged a beam of light to a race in the 100-meter dash.The race is held in a stadium full of spectators.At the start signal,a laser beam is turned on at the start line,pointed down the track.At the same instant,Ben bursts out of the starting blocks at 99% of the speed of light (0.99c).According to Ben,what happens?

Accepted Answer

A) The light beam gradually pulls ahead of him and wins the race because it is going 1% of the speed of light faster than him. 
B) The light beam instantly finishes the race,before Ben even has a chance to start. 
C) The light beam moves out ahead of him at the full speed of light,winning the race easily. 
D) Ben wins the race and becomes a hero.

Question 11

What do we mean by length contraction in relativity?

Accepted Answer

A) It is the idea that if you measure the size of an object moving relative to you,you will find that it is shorter in every direction than it would be at rest.That is,length,width,and height are all shorter for an object when it is moving by you. 
B) It is the idea that moving objects look smaller than nonmoving objects,but their sizes have not really changed. 
C) It is the idea that if you measure the size of an object moving relative to you,you will find that in the direction of motion it is shorter than it would be at rest,while its size in other directions is unchanged. 
D) It is the idea that if you travel very fast,you'll notice yourself getting shorter.

Question 12

Al is moving by you at a very high speed (close to the speed of light).You get out a clock and measure 10 seconds going by.If you also watch a clock in Al's ship,how much time will you see it record during your 10 seconds?

Accepted Answer

A) Al's clock will record less than 10 seconds. 
B) Al's clock will record more than 10 seconds. 
C) Al's clock will agree that 10 seconds go by.

Question 13

Different observers always agree about the order of events that occur at the same place.

Accepted Answer

A) True 
 B)False

Question 14

The surface of Earth is an example of a free-float reference frame.

Accepted Answer

A) True 
 B)False

Question 15

Suppose your normal resting heart rate is 60 beats per minute.Now,suppose you board a spaceship that travels away from Earth at 90% of the speed of light.While on the ship,you measure your heart rate.What will it be?

Accepted Answer

A) It will be 46 beats per minute. 
B) It will be 74 beats per minute. 
C) It will still be 60 beats per minute. 
D) It will be 12 beats per minute.

Question 16

The picture below shows a sphere as it looks at rest.Suppose the sphere is moving to the right at about 90 percent of the speed of light. 
Which figure below correctly shows the shape of the sphere as you would measure it?

Accepted Answer

A) Figure A 
B) Figure B 
C) Figure C 
D) Figure D 
E) Figure E

Question 17

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 the speed of light is relative,and depends on who is measuring it. 
C) The theory says that truth can never be established in any absolute sense. 
D) The theory says that measurements of motion make sense only when we state what they are measured relative to.

Question 18

The measured value of the speed of light is about 300,000 km/s.Suppose a futuristic space train is traveling at 200,000 km/s with its headlights on.If you could measure the speed of the light from the headlights,you would find it to be

Accepted Answer

A) 200,000 km/s. 
B) 100,000 km/s. 
C) 300,000 km/s. 
D) 500,000 km/s.

Question 19

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

Question 20

In relativity,two people share the same frame of reference only if

Accepted Answer

A) they are not moving relative to each other. 
B) they are both located in the same place. 
C) they are both located in the same place and are traveling at the same speed. 
D) they are both located in the same place and are stationary. 
E) they agree on the laws of nature.

Exam 26: Space and Time

Describe at least three pieces of evidence supporting the special theory of relativity.

Explain why relativity allows us to travel,in principle,to the center of the Milky Way,but we would never be able to tell our friends back home about it.

A spaceship is moving past you at a speed very close to the speed of light.If you could somehow watch the people inside it over a long period of time,what would you conclude?

The general theory of relativity deals with the effects of gravity,but the special theory of relativity does not take gravity into account.

A man is moving by you at a speed close to the speed of light.Which of the following correctly summarizes the effects you would notice on his mass,size,and time?

If you see Al going to your left at exactly 0.99c and Bob going to your right at exactly 0.99c,Al will say that Bob is

In what way do observations of binary star systems support the special theory of relativity?

The fact that we cannot travel faster than the speed of light means that it is theoretically impossible for us to make trips to distant stars within our lifetimes.

What do we mean by length contraction in relativity?

Al is moving by you at a very high speed (close to the speed of light) .You get out a clock and measure 10 seconds going by.If you also watch a clock in Al's ship,how much time will you see it record during your 10 seconds?

Different observers always agree about the order of events that occur at the same place.

The surface of Earth is an example of a free-float reference frame.

Suppose your normal resting heart rate is 60 beats per minute.Now,suppose you board a spaceship that travels away from Earth at 90% of the speed of light.While on the ship,you measure your heart rate.What will it be?

The picture below shows a sphere as it looks at rest.Suppose the sphere is moving to the right at about 90 percent of the speed of light. Which figure below correctly shows the shape of the sphere as you would measure it?

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

The measured value of the speed of light is about 300,000 km/s.Suppose a futuristic space train is traveling at 200,000 km/s with its headlights on.If you could measure the speed of the light from the headlights,you would find it to be

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

In relativity,two people share the same frame of reference only if