What is proper time?
a. Proper time is the time measured by a clock at rest with respect to the observer.
b. Proper time is time based on your actual longitude, not your time zone.
c. Proper time is the time given on your GPS.
d. Proper time means standard time as opposed to daylight savings time.
[Ques. 2] An astronaut is traveling at a high rate of speed from the Earth to a distant star system. Observers here on Earth note the relativistic effect that the astronaut's clocks run slow. What relativistic effect, if any, does the astronaut observe?
a. Her pulse rate slows.
b. The distance from the Earth to the star system has decreased. c. Her clocks run faster.
d. There is no relativistic effect to be observed by the astronaut since she is the one doing the moving.
[Ques. 3] If astronauts could travel at v = 0.90c, we on Earth would say it takes (4.2/0.90) = 4.7 years to reach Alpha Centauri, 4.2 lightyears away. The astronauts disagree. How much time passes on the astronaut's clocks?
a. 2.0 years
c. 1.4 years
b. 2.4 years
d. 3.0 years
[Ques. 4] A muon formed high in the Earth's atmosphere travels at a speed 0.990c for a distance of 6.40 km before it decays. What is the muon's lifetime as measured in its reference frame?
a. 4.65 10-6 s
c. 2.18 10-6 s
b. 1.55 10-5 s
d. 3.04 10-6 s
[Ques. 5] At what speed would a clock have to be moving in order to run at a rate that is one-third the rate of a clock at rest?
a. 0.97c
c. 0.87c
b. 0.75c
d. 0.94c
[Ques. 6] A boxcar without a front or a back is moving toward the right. Two electrons move through the boxcar, one moving from back to front toward the right, the other moving from front to back toward the left. According to me, each electron is moving with a speed of 0.8c, and the boxcar is moving with a speed of 0.6c. A passenger in the boxcar records how long it takes each electron to pass from one end of the boxcar to the other end. According to the passenger, which took less time?
a. the electron going from front to back
b. the electron going from back to front
c. Since nothing can go faster than light, an electron cannot move toward the left with a speed of 0.8c through a boxcar moving toward the right with a speed of 0.6c. d. They both took the same time.
[Ques. 7] A boxcar without a front or a back is moving toward the right. Two flashes of light move through the boxcar, one moving from back to front toward the right, the other moving from front to back toward the left. A passenger in the boxcar records how long it takes each flash of light to pass from one end of the boxcar to the other end. According to the passenger, which took longer?
a. the flash going from back to front
b. the flash going from front to back
c. They both took the same time.
d. It depends on whether the passenger is sitting at the front or the back of the boxcar.
[Ques. 8] From a stationary position, I observe a moving boxcar, which has a mirror along the front wall, but it is open at the back of the boxcar. I send a flash of light from my flashlight and time the flash of light as it goes to the front of the boxcar and returns to the back of the boxcar. A passenger in the boxcar also times the round trip of the flash of light. Previously I had measured the time required for the round trip of a flash of light when the boxcar was stationary, and I call this the stationary time. Which two times are the same?
a. the time recorded on the passenger's watch and the previous stationary time
b. the time recorded on my watch and the time recorded on the passenger's watch
c. the time recorded on my watch and the previous stationary time
d. None of the times are the same.
[Ques. 9] From a stationary position, I observe a moving boxcar, which has a mirror along the front wall, but it is open at the back of the boxcar. I send a flash of light from my flashlight and time the flash of light as it goes to the front of the boxcar and returns to the back of the boxcar. A passenger in the boxcar also times the round trip of the flash of light. Compare the times recorded on our watches.
a. The time recorded on the two watches is the same.
b. The time recorded on his watch is shorter.
c. The time recorded on his watch is longer.
d. The answer depends on the reference system you are in.
[Ques. 10] The astronaut whose heart rate on Earth is 60 beats/min increases his velocity to v = 0.60c. Now what is his heart rate as measured by an Earth observer?
a. 100 beats/min
c. 36 beats/min
b. 75 beats/min
d. 48 beats/min
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