University Physics Wolfgang Bauer Gary Westfall Chapter 35
University Physics Wolfgang Bauer Gary Westfall Chapter 35 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.
35. 1 In-Class Exercise An event 0 takes place at some point in space-time, as shown in the figure. Which of the five other events A, B, C, D, E in space-time can be influenced by the event 0? Check all that apply! A) B) C) D) E)
35. 2 In-Class Exercise An event 0 takes place at some point in spacetime, as shown in the figure. Which of the five other events A, B, C, D, E in space-time form a time-like space-time interval with the event 0? Check all that apply! A) B) C) D) E)
35. 3 In-Class Exercise A clock on a spaceship shows that a time interval of 1. 00 s has expired. If this clock is observed moving with a speed of 0. 860 c, what time period has expired in the frame of the stationary observer? a) 0. 860 s b) 1. 00 s c) 1. 25 s d) 1. 77 s e) 1. 96 s
35. 4 In-Class Exercise State whether each of the following statements is true or false. a) For a moving object, its length along the direction of motion is shorter than when it is at rest. b) When you are stationary, a clock moving past you at a significant fraction of the speed of light seems to run faster than the watch on your wrist. c) When you are moving with a speed that is a significant fraction of the speed of light, and you pass by a stationary observer, you observe that your watch seems to be running faster than the watch of the stationary observer.
35. 5 In-Class Exercise The nearest star to us other than the Sun is Proxima Centauri, which is 4. 22 light-years away. Suppose we had a spaceship that could travel at a speed of 90. 0% of the speed of light. If you were in the spaceship, how long would it take for you to travel from the Sun to Proxima Centauri, from your point of view? a) 2. 04 years b) 2. 29 years c) 3. 42 years d) 3. 80 years e) 4. 22 years
35. 6 In-Class Exercise Which of the following are invariants under the classical Galilean transformation of equation 35. 14? (Mark all that apply!) a) x b) y c) z d) t
35. 7 In-Class Exercise We have just seen that the real sum of two positive velocities consistent with relativity is less than that resulting from classical velocity addition. What about velocity differences? Assume that two velocity vectors and both point in the positive x-direction. Call the relative velocity between the two. Which of the following is correct? a) b) c) d) Can be either (a) or (c), depending on which of the two velocities and is larger.
35. 8 In-Class Exercise What is the Schwarzschild radius of a black hole with a mass of 14. 6 solar masses (msun = 1. 99 · 1030 kg)? a) b) c) d) e) 43. 2 cm 55. 1 m 1. 55 km 43. 1 km 4. 55 · 104 km
Answer Key – Chapter 35 35. 1 35. 2 35. 3 35. 4 35. 5 35. 6 35. 7 35. 8 C, D, E A, C, D, E e a) true b) false c) true a b, c, d a d
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