question

In relativity, two people share the same reference frame only if what is true?

answer

they are not moving relative to each other

question

You can see a clock in a spaceship moving past you at 90 percent of the speed of light. According to you, how much time would pass while the clock in the spaceship ticked through one minute?

answer

more than one minute

question

You and Mae are in free-float frames. Mae has just passed you, traveling at a speed of 60 km/hr. You throw a ball toward her at a speed of 60 km/hr. What will Mae see the ball doing?

answer

The ball will be stationary, floating freely in her own reference frame

question

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 ______.

answer

300,000 km/s

question

Which of the following is not relative in the special theory of relativity?

answer

the speed of light

question

Which of the following must be true of a person who shares the same reference frame as you?

answer

The person must not be moving relative to you

question

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?

answer

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.

question

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?

answer

The two bolts of lightning struck at different times, and they struck at places that are less than a mile apart.

question

Kim is in a spaceship moving past you at half the speed of light. Which of the following correctly describes how you will perceive each other's time?

answer

You will say that Kim's time is running slow, and she will say that your time is running slow.

question

Which of the following best describes why your rocket could never reach the speed of light?

answer

The absoluteness of the speed of light means you could never keep up with the light coming from you and your rocket.

question

A subatomic particle that normally decays in 1 microsecond is created in a particle accelerator and is traveling at close to the speed of light. If you measure its lifetime in that case, you'll find that it is

answer

more than 1 microsecond

question

If you observe people moving by you at very high speed, you will say that their time runs slowly, their lengths are contracted in the direction of motion, and their masses are increased from their rest masses. What will they say about you?

answer

Your time runs slowly, your length is contracted in the direction of motion, and your mass is increased from your rest mass.

question

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 lightâ€”say, 0.9999c. According to Gwen back on Earth, about how long does it take Jackie to reach Vega?

answer

about 25 years

question

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?

answer

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

Again consider two twin sisters, Gwen and Jackie, who are both 20 years old in the year 2020. This time, assume that Jackie makes the round-trip to Vega, which is 25 light-years away, at an average speed of 0.9999c. Which of the following correctly describes the situation when Jackie returns to Earth? (Ages in this problem refer to biological agesâ€”that is, how much time has passed for each sister since she was born.)

answer

It's the year 2070. Gwen (who stayed home) is 70 years old, but Jackie is only a little older than her age of 20 when she left.

question

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

answer

1. The laws of nature are the same for everyone.2. The speed of light is the same for everyone

question

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

answer

the nature of gravity

question

Carla is traveling past you at a speed close to the speed of light. According to you, how much time passes for Carla while 1 minute passes for you?

answer

less than 1 minute

question

Carla is traveling past you at a speed close to the speed of light. According to her, how much time passes for you while 1 minute passes for her?

answer

less than one minute

question

What does the famous formula E=mc2 have to do with special relativity?

answer

It is a direct consequence of the theory.

question

What provides the strongest evidence that everyone always measures the same speed of light?

answer

Precise measurements of the speed of light under different circumstances

question

Suppose you had a spaceship so fast that you could make a roundtrip journey of 1 million light-years (in Earth's reference frame) in just 50 years of ship time. If you left in the year 2030, you would return to Earth

answer

a million years from now

question

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

answer

1. The laws of nature are the same for everyone.2. The speed of light is the same for everyone

question

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

answer

The theory says that measurements of motion make sense only when we state what they are measured relative to.

question

Which of the following is not a prediction made by the theory of relativity?

answer

Observers in different reference frames may disagree about the basic laws of nature.

question

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

answer

does not violate our common sense.

question

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

answer

they are not moving relative to each other

question

You and Al are both floating freely in your spaceships. Suppose 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?

answer

He sees you moving away from him at 85 km/hr and the ball moving away from him at 10 km/hr.

question

Bob is coming toward you at a speed of 75 km/hr. You throw a baseball in his direction at 75 km/hr. What does he see the ball doing?

answer

He sees the ball coming at him at 150 km/hr.

question

Shawn is traveling away from you at a speed of 120 km/hr. He throws a baseball that, according to him, is going at 100 km/hr in your direction. What do you see the ball doing?

answer

You see the ball traveling away from you at 20 km/hr.

question

Sue is traveling toward you at 90 km/hr. She throws a baseball that, according to her, is going at 90 km/hr in the opposite direction. What do you see the ball doing?

answer

You see the ball remaining stationary.

question

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?

answer

Carol sees Sam going away from her at 165 km/hr.

question

You are racing away from Earth in a super spaceship in which you can continually increase your speed. Which of the following best explains how people on Earth will perceive your speed?

answer

You will see any beam of light from Earth coming toward you at the speed of light, which means it will catch you. Thus, the people on Earth must conclude that you are going slower than the speed of light.

question

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

answer

going away from her faster than 0.99c, but slower than c

question

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?

answer

quite a bit less than 4 light years

question

A spaceship is moving past us at a speed close to the speed of light.How would we view time (clocks) on the spaceship as it goes by?

answer

Their clocks are going slower than ours.

question

A spaceship is moving past us at a speed close to the speed of light.If we could measure the mass of the spaceship as it goes by, what would it be?

answer

Its mass is greater than its rest mass.

question

A spaceship is moving past us at a speed close to the speed of light. How would the passengers on the spaceship view our clocks?

answer

our clocks going slow

question

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?

answer

al's clock will record less than 10 seconds

question

Twin sisters, Gwen and Jackie, were both 20 years old in the year 2000. Jackie took off on a round trip to Vega, 25 light-years away. She traveled at an average speed very close to the speed of lightâ€”say, 0.9999c. According to Gwen back on Earth, about how long does it take Jackie to reach Vega?

answer

about 25 years