Inertial Reference Frames and Events Timing

1. Chapter 36

2. Which of these is an inertial reference frames (or a very good approximation)? 1. A car rolling down a steep hill 2. A rocket being launched 3. A roller coaster going over the top of a hill 4. A sky diver falling at terminal speed 5. None of the above

3. Which of these is an inertial reference frames (or a very good approximation)? 1. A car rolling down a steep hill 2. A rocket being launched 3. A roller coaster going over the top of a hill 4. A sky diver falling at terminal speed 5. None of the above

4. Ocean waves are approaching the beach at 10 m/s. A boat heading out to sea travels at 6 m/s. How fast are the waves moving in the boat’s reference frame? 1. 4 m/s 2. 6 m/s 3. 10 m/s 4. 16 m/s

5. Ocean waves are approaching the beach at 10 m/s. A boat heading out to sea travels at 6 m/s. How fast are the waves moving in the boat’s reference frame? 1. 4 m/s 2. 6 m/s 3. 10 m/s 4. 16 m/s

6. A carpenter is working on a house two blocks away. You notice a slight delay between seeing the carpenter’s hammer hit the nail and hearing the blow. At what time does the event “hammer hits nail” occur? 1. At the instant you hear the blow. 2. At the instant you see the hammer hit. 3. Very slightly after you see the hammer hit. 4. Very slightly after you hear the hammer hit. 5. Very slightly before you see the hammer hit.

7. A carpenter is working on a house two blocks away. You notice a slight delay between seeing the carpenter’s hammer hit the nail and hearing the blow. At what time does the event “hammer hits nail” occur? 1. At the instant you hear the blow. 2. At the instant you see the hammer hit. 3. Very slightly after you see the hammer hit. 4. Very slightly after you hear the hammer hit. 5. Very slightly before you see the hammer hit.

8. A tree and a pole are 3000 m apart. Each is suddenly hit by a bolt of lightning. Mark, who is standing at rest midway between the two, sees the two lightning bolts at the same instant of time. Nancy is at rest under the tree. Define event 1 to be “lightning strikes tree” and event 2 to be “lightning strikes pole.” For Nancy, does event 1 occur before, after or at the same time as event 2? 1. at the same time as event 2 2. before event 2 3. after event 2

9. A tree and a pole are 3000 m apart. Each is suddenly hit by a bolt of lightning. Mark, who is standing at rest midway between the two, sees the two lightning bolts at the same instant of time. Nancy is at rest under the tree. Define event 1 to be “lightning strikes tree” and event 2 to be “lightning strikes pole.” For Nancy, does event 1 occur before, after or at the same time as event 2? 1. at the same time as event 2 2. before event 2 3. after event 2

10. A tree and a pole are 3000 m apart. Each is suddenly hit by a bolt of lightning. Mark, who is standing at rest midway between the two, sees the two lightning bolts at the same instant of time. Nancy is flying her rocket at v = 0.5c in the direction from the tree toward the pole. The lightning hits the tree just as she passes by it. Define event 1 to be “lightning strikes tree” and event 2 to be “lightning strikes pole.” For Nancy, does event 1 occur before, after or at the same time as event 2? 1. at the same time as event 2 2. before event 2 3. after event 2

11. A tree and a pole are 3000 m apart. Each is suddenly hit by a bolt of lightning. Mark, who is standing at rest midway between the two, sees the two lightning bolts at the same instant of time. Nancy is flying her rocket at v = 0.5c in the direction from the tree toward the pole. The lightning hits the tree just as she passes by it. Define event 1 to be “lightning strikes tree” and event 2 to be “lightning strikes pole.” For Nancy, does event 1 occur before, after or at the same time as event 2? 1. at the same time as event 2 2. before event 2 3. after event 2

12. Molly flies her rocket past Nick at constant velocity v. Molly and Nick both measure the time it takes the rocket, from nose to tail, to pass Nick. Which of the following is true? 1. Both Molly and Nick measure the same amount of time. 2. Nick measures a shorter time interval than Molly. 3. Molly measures a shorter time interval than Nick.

13. Molly flies her rocket past Nick at constant velocity v. Molly and Nick both measure the time it takes the rocket, from nose to tail, to pass Nick. Which of the following is true? 1. Both Molly and Nick measure the same amount of time. 2. Nick measures a shorter time interval than Molly. 3. Molly measures a shorter time interval than Nick.

14. Beth and Charles are at rest relative to each other. Anjay runs past at velocity v while holding a long pole parallel to his motion. Anjay, Beth, and Charles each measure the length of the pole at the instant Anjay passes Beth. Rank in order, from largest to smallest, the three lengths LA, LB, and LC. 1. LA > LB = LC 2. LA = LB = LC 3. LA > LB > LC 4. LB = LC > LA 5. LB > LC > LA

15. Beth and Charles are at rest relative to each other. Anjay runs past at velocity v while holding a long pole parallel to his motion. Anjay, Beth, and Charles each measure the length of the pole at the instant Anjay passes Beth. Rank in order, from largest to smallest, the three lengths LA, LB, and LC. 1. LA > LB = LC 2. LA = LB = LC 3. LA > LB > LC 4. LB = LC > LA 5. LB > LC > LA

16. An electron moves through the lab at 99% the speed of light. The lab reference frame is S and the electron’s reference frame is S´. In which reference frame is the electron’s rest mass larger? 1. Frame S, the lab frame 2. Frame S´, the electron’s frame 3. It is the same in both frames.

17. An electron moves through the lab at 99% the speed of light. The lab reference frame is S and the electron’s reference frame is S´. In which reference frame is the electron’s rest mass larger? 1. Frame S, the lab frame 2. Frame S´, the electron’s frame 3. It is the same in both frames.

18. Chapter 36 Reading Quiz

19. In relativity, the Galilean transformations are replaced by 1. Einstein tranformations. 2. Lorentz transformations. 3. Feynman transformations. 4. Maxwell transformations. 5. Laplace tranformations.

20. In relativity, the Galilean transformations are replaced by 1. Einstein tranformations. 2. Lorentz transformations. 3. Feynman transformations. 4. Maxwell transformations. 5. Laplace tranformations.

21. A physical activity that takes place at a definite point in space and time is called 1. a gala. 2. a sport. 3. an event. 4. a happening. 5. a locale.

22. A physical activity that takes place at a definite point in space and time is called 1. a gala. 2. a sport. 3. an event. 4. a happening. 5. a locale.

23. Which of these topics was not discussed in this chapter? 1. Teleportation 2. Simultaneity 3. Time dilation 4. Length contraction

24. Which of these topics was not discussed in this chapter? 1. Teleportation 2. Simultaneity 3. Time dilation 4. Length contraction

25. Proper time is • 1. the time calculated with the correct relativistic expression. • 2. the longest possible time interval between two events. • 3. a time interval that can be measured by a single clock. • 4. the time measured by a light clock • 5. not discussed in Chapter 36.

26. Proper time is • 1. the time calculated with the correct relativistic expression. • 2. the longest possible time interval between two events. • 3. a time interval that can be measured by a single clock. • 4. the time measured by a light clock • 5. not discussed in Chapter 36.