##### # Unit 7, Quiz #1 1. Suppose the time taken for light to bounce to and fro between the parallel mirrors of a light clock is 1 second, in the frame of reference of this light clock. If the light clock were moving at a relativistic speed relative to an observer on earth, the time as observed from earth would be a. also 1 second. b. less than 1 second. c. more than 1 second.   2. When a blinking light source moves towards you, its speed changes but its frequency remains constant. remains constant, but its frequency can change. stays the same, as does its frequency.   3. According to special relativity, as the rate at which a person travels through space increases, the rate at which they travel through time __________. increases decreases is not changed   4. A woman standing on the ground sees a rocket ship move past her at 95% the speed of light. compared to when the rocket is at rest, the woman measures the rocket's length as a. longer. b. shorter. c. the same length.   5. When an object is pushed to relativistic speeds, its mass is a. greater than at rest. b. smaller than at rest. c. the same as at rest.   6. An astronaut boards a 100-m long rocket. When traveling past earth at relativistic speeds, occupants of earth tell her that the ship appears contracted in length. If the astronaut were to measure the length of her own rocket, then she would measure the length to be a. less than 100 m b. more than 100 m c. exactly 100 m   7. A spaceship that is traveling very fast with respect to your frame of reference, fires a light beam that travels at speed c with respect to the spaceship. You measure the light beam's speed to be a. less than c b. more than c c. equal to c   8. It is theoretically possible for a person to be biologically older than his own parents by traveling to a very distant destination and back at relativistic speeds. sending his/her parents to a very distant destination and back at relativistic speeds. ... nonsense! This would never be possible even according to Einstein's theories. taking many more physics courses so that he/she can become wiser and therefore older.   9. According to Einstein, it is theoretically impossible for an object to be pushed to a speed equal to the speed of light because ______. the object would become lost from our sight as it moves faster the mass of the object would decrease and require an infinite force to push it to higher speeds the mass of the object would increase and require an infinite force to push it to higher speeds ... nonsense! It is theoretically possible; we just haven't developed the technology to do it.   10. According to special relativity, one could travel through time at decreased rates by a. moving slower. b. moving faster. c. pushing the snooze button. d. ... nonsense! Relativity says nothing about time.   11. Ima Rushin is moving at 99.99% the speed of light relative to a stationary reference frame. Calculate the length of her 2-meter stick as viewed from the stationary reference frame. PSYW     12. The plot of a science fiction novel hinges on the possibility that the main character travels back into the future to perform good acts and become a hero. Would such a plot be plausible according to Einstein's theory of relativity? Reveal your understanding of Einstein's thoughts on time travel by discussing this question.         13. Discuss how Einstein's conceptions of the physical world differ than Galilean or Newtonian conceptions of the physical world. In your discussion, make reference to the following two diagrams.       14. Suppose in another world the speed of light were 10 m/s, the speed of a fast runner. Using complete sentences, describe some effects on Olympic Game events (sprints, long-distance runs, pole-vaulting, high jumping, etc.) in this world. Be as specific and descriptive as possible.       ### Useful Web Links Information on the topic of relativity can be found at The Physics Classroom. Additionally, animations and an interactive Shockwave movie can be found at the Multimedia Physics Studios and at the Shockwave Physics Studios.
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