AST201-A

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

Which of the following statements best describes what is "relative" in the theory of relativity? A. The theory says that measurements of motion make sense only when we state what they are measured relative to. 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 everything is relative.

In relativity, two people share the same reference frame only if what is true? A. They agree on the laws of nature. B. They are both located in the same place. C. They are not moving relative to one another. D. They are both located in the same place and are stationary.

You are in an airplane, traveling relative to the ground at 500 km/hr. You throw a baseball toward the front of the plane at a speed of 50 km/hr. How fast would someone on the ground say the baseball is moving?

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?

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 ______.

What do we mean by time dilation in relativity?

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

What do we mean by length contraction in relativity?

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?

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 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?

Consider the same scenario as in a 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?

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 ages, that is, how much time has passed for each sister since she was born.)

Which of the following is NOT true of the special theory of relativity? A. The theory tells us that there is no such thing as absolute time or space because measurements of time and space depend on your reference frame. B. The special theory does not apply to situations that involve substantial acceleration or gravity; for that, you need the general theory of relativity. C. The theory is valid only at speeds close to the speed of light. D. For low speeds, the theory predicts effects that are so small that they cannot be noticed without extremely precise, high-tech measurement.

An airplane traveling east to west along Earth's equator at the same speed that Earth rotates from west to east. Viewed from the Moon, what does the airplane do?

People on Earth would, of course, simply see the airplane fly westward at 1,670 km/hr. What is the significance of the difference in viewpoints between people on Earth and people on the Moon?

You've just thrown a baseball toward Al at 100 km/hr, while he is moving away from you to the right at 90 km/hr. According to Al, what is the baseball doing?

You've just shined a flash light toward Al, so from your point of view the light is moving to the right at speed c. Al is moving away from you to the right at speed 0.9c. According to Al, what is the light doing?

A person on a planet watching you travel to the right at 0.9c, while you have a flashlight turned on with the light shining to the right. Which of the following statements is NOT true from your point of view?

Suppose that the sphere is moving to the right at about 90% of the speed of light. What is the shape of the sphere are you would measure it?

The observation that you will measure the length of an object moving relative to you as being shorter than the same object at rest is an example of _____.

The _____ applies even to cases in which gravity or accelerations are present.

An observer on the Moon would observe astronauts on a spaceship passing by at 0.9c to age more slowly due to -----.

When the Space Shuttle and Space Station are docked to each other, astronauts in these two spacecraft will make the same measurements about space and time because they are in the same ____.

A situation that at first does not seem to make sense is a _____.

The _____ tells us that we see time run more slowly in other reference frames besides our own.

Astronauts are weightless in the International Space Station because they are in a _____.

In relativity, two people share the same reference frame only if what is true? A. They are both located in the same place. B. They agree on the laws of nature. C. They are not moving relative to one another. D. They are both located in the same place and are stationary.

Which of the following is not relative in the special theory of relativity? A. motion B. time C. the speed of light

Which of the following must be true of a person who shares the same reference frame as you? A. The person must be sitting right next to you. B. The person must be the same size as you. C. The person must not be moving relative to you.

You see Jackie's spaceship traveling at 1000 km/hr as she throws the baseball at a speed of 100 km/hr. How fast would you say the baseball is going?

You see Jackie's spaceship traveling at 1000 km/hr, with the ship's headlight on. According to special relativity, Jackie would say that a beam of light from the headlight is traveling at __________, and you would say that the beam of light is traveling at __________.

You see Jackie's spaceship traveling at 0.99c. This time, Jackie would say that a beam of light from the headlight is traveling at __________ and you would say that the beam of light is traveling at __________.

Jackie has her spaceship engines on, so that she accelerates continuously. As she accelerates, Jackie would say that __________ and you would say that __________.

Based on these thought experiments, what can you conclude? A. Jackie would have to accelerate for a very long time before she finally reaches the speed of light. B. Jackie will say that she is going faster than light, but you'll always say she's going slower than the speed of light. C. You can see Jackie going faster than light, but she'll never say she's going that fast. D. Jackie can never reach or exceed the speed of light.

In science, it is now well accepted that the speed of light is always the same and therefore nothing can travel faster than light. These ideas gained acceptance primarily because __________.

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

Consider again the spaceships from Parts A and B. Suppose that, at rest, both you and a passenger on the other spaceship have the same heart rate of 60 beats per minute. How will you and the passenger on the other spaceship observe each other's heart rates as you pass by in your spaceships?

Each figure below shows a spaceship moving past your spaceship ("YOU") at the indicated speed. Imagine that you watch the other spaceship as its clock ticks off one second. Rank the figures according to how much time you would say passes (on your own ship) while the other ship's clock ticks off one second, from the shortest to the longest amount of time.

The four figures below are the same as those in Part A. This time, imagine that the passengers on the other spaceship are watching your clock as its ticks off one second. Rank the figures according to how much time the passengers (on the other ship) would say passes (on their ship) while they watch your clock tick off one second, from the shortest to the longest amount of time.

Suppose you had a spaceship so fast that you could make a round-trip 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

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?

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?

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?

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?

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? A. You may soon be racing away from Earth faster than the speed of light, but, if so, people on Earth will no longer be able to see you. B. An imaginary spaceship can go as fast as it wants, so the folks on Earth soon will see you going faster than the speed of light. C.Without more information, it is impossible to know how fast you would see a light beam from Earth coming toward you. If it happens that you are going fast enough so that the light can't catch you, then people on Earth would find you to be going faster than light. D. They will know you are going very fast but will have no way of knowing whether you ever exceed the speed of light. E. 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.

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 ...

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?

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?

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

Different observers can disagree about the speed of a baseball, but they cannot disagree about the speed of a light beam. A. True B. False

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?

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?

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?

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.

Which of the following will both you and an observer on Earth agree on as you travel through space in your spaceship? (More than one) A. You will both agree on exactly how much faster your light is moving than your spaceship is moving. B. You will both agree that you are traveling slower than your own light. C. You will both agree on your spaceship's speed. D. You will both agree that your light is traveling at the speed of light, or 300,000 km/s. E. You will both agree that you are moving through space while Earth is stationary.

What is time dilation?

What are the two absolutes of Relativity?

Which of the following most clearly explains why you must measure the time it takes the light to go from Al's floor to ceiling and back to be longer than the time that Al measures? A. You see the light traveling at a faster speed than Al does, becauase of his forward motion. B. You see the light travel a longer path, and you an Al both agree on the light's speed. C. You see the light travel a straighter path, and you an Al both agree on the light's speed. D. You see the light travel a shorter path, and you an Al both agree on the light's speed.

On the relativity of simultaneity. How would Al explain the fact that you are illuminated by the green and red lights at the same time, given that he saw the green light flash before the red light? A. You saw the red light flash first. B. You are moving toward the red light. C. You are moving toward the green light. D. It is inexplicable.

What is the Relativity of Simultaneity?

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. A. True B. False

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

The surface of Earth is an example of a free-float reference frame. A. True B. False

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?

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

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. According to Ben, what happens? A. The light beam gradually pulls ahead of him and wins the race because it is going 1 percent 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.

Einstein's equivalence principle says that ______.

Alice is floating freely in her spacecraft, and you are accelerating away from her with an acceleration of 1g. How will you feel in your spacecraft?

Alice is floating freely in her spacecraft, and you are accelerating away from her with an acceleration of 1g. Suppose you claim that you are feeling the effects of a gravitational field. How can you explain the fact that Al is weightless?

Imagine that you are sitting in a closed room (no windows, no doors) when, magically, it is lifted from Earth and sent accelerating through space with an acceleration of 1g (9.8 m/s2). According to Einstein's equivalence principle, which of the following is true? A. You'll know that you left Earth because you'll be floating weightlessly in your room. B. You'll feel a force that will cause your head to repeatedly bang into the ceiling. C. You'll know that you left Earth because when you drop a ball it will fall sideways. D. You won't feel any change and will have no way to know that you've left Earth.