Relativity Questions

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Relativity Questions
Chris Parkes

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Motion
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Q37.1
As a high-speed spaceship flies past you at half
the speed of light, it fires a strobe light. An
observer on board the spaceship measures a
spherical wave front that spreads away from the
strobe light with the same speed c in all
directions. The wave front that you measure
1. is spherical and remains centered on the
spaceship as it moves 2. is spherical and is
centered on the point where the spaceship was
when the strobe was fired 3. is not spherical but
remains centered on the spaceship as it moves 4.
is not spherical but is centered on the point
where the spaceship was when the strobe was fired
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Q37.5
Santiago stands on the ground as Miriam flies
directly toward him in her spaceship at 0.5c. She
fires a small rocket directly toward Santiago
that flies at a speed of 0.8c relative to her
spaceship. According to Santiago, the speed of
the rocket is
1. 1.3c 2. faster than c but slower than 1.3c 3.
c 4. faster than 0.8c but slower than c 5. 0.8c
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Q37.2
simultaneity
A high-speed train is traveling from Glasgow to
Edinburgh. According to an observer at rest on
the ground, the clocks at the railroad stations
in Glasgow and Edinburgh both strike noon at the
same time. According to a passenger on the train,
when the Glasgow clock strikes noon, what time is
it in Edinburgh?
1. noon 2. before noon 3. after noon 4. answer
depends on the speed of the train
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Glasgow
Edinburgh
Moving towards Edinburgh noon clock Moving away
from Glasgow noon clock
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Time dilation length Contraction Lorentz
transforms
Q37.4
Samir (who is standing on the ground) starts his
stopwatch at the instant that Maria flies past
him in her spaceship. At the instant that Samirs
stopwatch reads 8.0 s, Marias stopwatch reads
10.0 s. According to Maria, her spaceship is 100
m long (along the direction of motion). According
to Samir, the length of her spaceship is
1. 64 m 2. 80 m 3. 100 m 4. 125 m 5. none of
the above
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Lorentz transforms
Q37.3
Samir (who is standing on the ground) starts his
stopwatch at the instant that Maria flies past
him in her spaceship. According to Maria, at the
instant that Samirs stopwatch reads 16.0 s,
Marias stopwatch reads 20.0 s. According to
Samir, at the instant that Marias stopwatch
reads 20.0 s, Samirs stopwatch reads
1. 16.0 s 2. 20.0 s 3. 25.0 s 4. none of the
above
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Q37.6
According to the relativistic expression for
momentum, if the speed of an object is doubled,
the magnitude of the momentum
1. increases by a factor greater than 2 2.
increases by a factor of 2 3. increases by a
factor greater than 1 but less than 2 4. answer
depends on the value of the initial speed