ASTR 1401 Chapter 7 – Flashcards

Each of the following lists two statements. Which two are the basic premises for the special theory of relativity? 1. The laws of nature are the same for everyone. 2. The speed of light is the same for everyone. 1. Everything is relative. 2. You can never really tell who is moving. 1. The speed of light is the same for everyone. 2. You can't go faster than the speed of light. 1. You can't go faster than the speed of light. 2. Time is different for different people. 1. The laws of nature are the same for everyone. 2. Everything is relative.

Which of the following statements best describes what is "relative" in the theory of relativity? The theory says that truth can never be established in any absolute sense. The theory says that the speed of light is relative and depends on who is measuring it. The theory says that everything is relative. The theory says that measurements of motion make sense only when we state what they are measured relative to. The theory says that all scientific results must be considered within the context of the scientists' individual viewpoints.

In relativity, two people share the same frame of reference only if they are both located in the same place and are stationary. they are both located in the same place and are traveling at the same speed. they agree on the laws of nature. they are both located in the same place. they are not moving relative to each other.

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? He sees the ball coming at him at 75 km/hr. He sees the ball going away from him at 150 km/hr. He sees the ball remaining stationary. He sees the ball going away from him at 75 km/hr. He sees the ball coming at him at 150 km/hr.

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? You see the ball traveling away from you at 120 km/hr. You see the ball traveling away from you at 220 km/hr. You see the ball traveling away from you at 20 km/hr. You see the ball traveling away from you at 100 km/hr. You see the ball traveling toward you at 20 km/hr.

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? Carol sees Sam going away from her at 90 km/hr. Carol sees Sam going away from her at 75 km/hr. Carol sees Sam going away from her at 165 km/hr. Carol sees Sam coming toward her at 15 km/hr. Carol sees Sam going away from her at 15 km/hr.

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? 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. 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. 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. They will know you are going very fast but will have no way of knowing whether you ever exceed the speed of light. 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.

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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? quite a bit more than 4 light-years very slightly more than 4 light-years quite a bit less than 4 light-years also about 4 light-years very slightly less than 4 light-years

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? Its mass is infinite. Its mass is less than its rest mass. Its mass is greater than its rest mass. Its mass is the same as it would be if it were not moving.

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? Our clocks are going slow. Our clocks are going at the same rate as theirs. Our clocks are going fast. They can't see our clocks, but we can see theirs. Time is the same for everyone.

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 light — say, 0.9999c. According to Gwen back on Earth, about how long does it take Jackie to reach Vega? about 100 years about 10 years about 1,000 years about 25 years about a month

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 light — say, 0.9999c. Which of the following best describes the situation according to Jackie? She's taking a trip that takes 25 years from Earth to Vega. 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. 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. 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.

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

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 Ben, what happens? Ben wins the race and becomes a hero. 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. The light beam moves out ahead of him at the full speed of light, winning the race easily. The light beam instantly finishes the race, before Ben even has a chance to start.

The lifetime of a π + meson normally is 18 nanoseconds. In a large particle accelerator, scientists can create π + 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? The π + meson no longer decays and remains as a stable particle. The π + meson lasts 18 nanoseconds. The π + meson lasts much more than 18 nanoseconds. The π + meson lasts much less than 18 nanoseconds.

Which of the following is not predicted by Einstein's special theory of relativity? the equivalence of mass and energy time dilation length contraction the constancy of the speed of light no material object can reach or exceed the speed of light