A knight on horseback holds a 9.0-m lance. The horse can run at 0.75c. (It wins most of its races) How long will the lance appear to a person that is standing still on the ground as the horse runs past?
a. 6.0 m
b. 14 m
c. 9 m
d. 6.8 m
e. 4.5 m
[Ques. 2] 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. 3] The short lifetime of muons created in the upper atmosphere of the Earth would not allow them to reach the surface of the Earth unless their lifetime increased by time dilation. From the reference system of the muons, the muons can reach the surface of the Earth because
a. time dilation increases their velocity.
b. time dilation increases their energy.
c. length contraction decreases the distance to the Earth.
d. the relativistic speed of the Earth toward them is added to their velocity.
[Ques. 4] A meter stick moving in a direction parallel to its length appears to be only 43.6 cm long to an observer. What is the meter stick's speed relative to the observer? (c = 3.00 108 m/s)
a. 2.25 108 m/s
b. 1.69 108 m/s
c. 2.70 108 m/s
d. 1.31 108 m/s
e. 2.95 108 m/s
[Ques. 5] How fast would a rocket have to move past a ground observer if the latter were to observe a 9.4 length shrinkage in the rocket length? (c = 3.00 108 m/s)
a. 2.98 108 m/s
b. 2.72 108 m/s
c. 1.27 108 m/s
d. 0.420 108 m/s
e. 0.920 108 m/s
[Ques. 6] An Earth observer sees a spaceship at an altitude of 920 m moving downward toward the Earth at a speed of 0.690c. What is the spaceship's altitude as measured by an observer in the spaceship?
a. 1270 m
b. 512 m
c. 1650 m
d. 666 m
e. 635 m
[Ques. 7] A rocket ship is 87.0 m in length when measured before leaving the launching pad. What would its velocity be if a ground observer measured its length as 62.0 m while it is in flight? (c = 3.00 108 m/s)
a. 1.61 108 m/s
b. 2.14 108 m/s
c. 1.48 108 m/s
d. 2.10 108 m/s
e. 1.91 108 m/s
[Ques. 8] A space probe is 15.6 m in length when measured at rest. What length does an observer at rest measure when the probe is going by at a speed of 0.740c?
a. 23.2 m
b. 10.5 m
c. 8.0 m
d. 11.5 m
e. 21.1 m
[Ques. 9] The period of an oscillating weight on a spring in an inertial frame of reference is 2.5 s. What would be its speed if it were to move by an observer who measures its period as 3.4 s? (c = 3.00 108 m/s)
a. 1.5 l08 m/s
b. 2.0 108 m/s
c. 2.8 l08 m/s
d. 6.8 107 m/s
e. 1.3 108 m/s
[Ques. 10] The period of a pendulum is 1.5 s in a stationary inertial frame of reference. What is its period when measured by an observer moving at a speed of 0.75 c with respect to the inertial frame of reference?
a. 1.0 s
b. 3.4 s
c. 2.3 s
d. 3.0 s
e. 0.8 s
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