Unit 9 Practice Test Flashcards
The speed of light, c, has been experimentally calculated with great accuracy. Which of the following values of c is incorrect?
c = 186,000 mi/h
True or false?
If S1 is an inertial frame and S2 is moving at uniform velocity relative to S1, then S2 is also an inertial frame.
true
Consider two inertial frames S1 and S2 in relative motion. Which of the following does not apply to the state of motion of inertial frame S1? The answer choices are based on observations made by either an observer at rest in S1 or an observer watching S1 from another inertial frame S2.
The observer in S2 notes that S1 is changing speed uniformly.
Inertial frames S1 and S2 are moving relative to each other with uniform speed v. The coordinates of an event in S1 re (x1, t1) and the coordinates of the same event in S2 are (x2, t2). According to Galilean relativity, which of the following is the relationship between the coordinates of the event in the respective frames shown in the figure?
x2 = x1 + vt1 t2 = t1 = t
Tow observers, P and Q, witness a light flash as shown in the figure. They are in the same reference frame and at rest relative to the light source. Suppose a clock is palced at the location of the light flash and the clock reads time t0 at the time of the flash. If P and Q have their own clocks, when will they see the flash? Let dP be the distance from the light flash to P, dQ be the distance from the light flash to Q, and dP
P witnesses the flash at tP = t0 + dP/c and Q witnesses the flash at tQ = t0 + dQ/c
Two events, separated by distance d in the same reference frame, occur at the same time if they have the same clock reading. Imagine that every position in a reference frame is fixed with a clock, and each clock should read the same time at any given instant. But because light signals take a finite amount of time to travel, it is necessary to compensate for this time to synchronize the clocks.
Consider a master clock located at O and another clock located at position P at a distance of d meters. Suppose a light signal is sent from O at time 0. The goal is to synchronize the two clocks, that is, the two clocks should read the same time at any given instant. At which of the following times should the clock C 1 start running when the signal reaches there?
d/c
An observer O, at rest in an inertial frame, notes the clock readings of two events, A and B, located at positions as shown in the figure. O witnesses event A at time tA = t0 and event B at tB = t0 = 1/c. Which of the following is the correct order of occurrence of A and B according to observer O?
A and B occur at the same time.
Suppose two inertial frames, A and B, are moving at speeds (1/4)c and (1/2)c, respectively, relative to an observer O at rest. Compare the values of the g-factor in the time dilation equation as measure by O for A and B
gA < gB
According to the special theory of relativity, moving clocks slow down. Suppose two spaceships pass each other with a relative speed v. Which of the following statements is incorrect?
As the relative speed v decreases, the time dilation factor increases, and clocks in the moving spaceship slow down further.
In the rest frame, a muon’s life is 2.2 × 10−6 s. An observer encounters a muon that is moving with 0.9c. What will the muon’s life be to the observer?
5.1 × 10^−6 s
Suppose delta l0 is the proper length of a rocket. Which of the following is the length of the rocket as measured by an observer who sees the rocket whiz by with velocity v?
delta l = delta l0 / g
A physicist G measures the height of the atmosphere, starting from the ground to the top of the atmosphere where muons are created. In G’s reference frame, the height of the atmosphere is 10 km. Imagine a physicist, M, moving along a muon with speed 0.9c. Which of the following is the height of the atmosphere measured by M ?
4.4 km
A rocket ship, with proper length l0, moves with a speed v relative to an observer. How fast must the rocket move for the observer to measure half of the rocket’s proper length?
0.866c
delta t’ = g(delta t - v delta x / c^2)
Which of the following shows how to derive the time dilation relationship from the above relationship?
delta x = 0
Which of the following variables denotes the velocity of the reference frame?
v
