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Physics Test 4 Questions with Accurate Answers
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Exam of 8 pages for the course Relativity at Relativity (Physics Test 4)
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Physics Test 4Special Theory of relativity - answer- Developed by Einstein
- It is a theory created by Einstein that describes how time is affected by motion in
space at constant velocity, and how mass and energy are related.
- It describes those 2 observers, in uniform relative motion, perceive time and space
differently.
Time Dilation - answer- It was an idea proposed by Einstein that stated that time can be
stretched depending on the motion between the observer and the events being
observed.
- It occurs whenever we move through space, we to some degree alter our rate of
moving into the future.
- It is also known as "the stretching of time."
- A slowing of time in accordance with the theory of relativity that occurs in a system in
motion relative to an outside observer and that becomes apparent especially as the
speed of the system approaches that of light — called also time dilatation.
Space-time - answerIt is a term made up of two parts: Space and time.
Postulates - answerThey are two fundamental assumptions that the theory of special
relativity rests on.
What did the first postulate of special relativity state? - answer- It states that all the laws
on nature are the same in all uniformly moving frames of reference.
- It can assume our inability to detect a state of uniform motion.
What did the second postulate of special relativity state? - answer- It states that the
speed of light in empty space will always have the same value regardless of the motion
of the source or the motion of the observer.
- It assumes that the speed of light is constant at 300,000 km/s
- The ratio of space to time for light is the same for all who measure it.
The ratio of space to time for light .............................................. - answer..........is the
same for all who measure it.
What was the reasoning behind Albert Einstein's ideas? - answerEinstein reasoned that
all motion is relative and all frames of reference are unpredictable. An object cannot
measure its speed relative to empty space, but only relative to other objects.
, According to Einstein's formula, what is the relationship between mass, energy, and the
speed of light? - answerE = mc^2
What is the speed of light and why is it such an important concept in physics? What is
the formula? - answerThe speed of light is 3.00 x 10^8 m/sec. Nothing travels faster
than the speed of light.
Speed of light - answerIt is equal to 3.00 x 10^8 meters per second.
Relativity of simultaneity - answerIt is when two events that occurred simultaneously for
one observer were not simultaneous for another observer if the two observers had
relative motion to each other.
Length contraction - answer- It is when moving rulers are shortened in the direction of
motion.
- It is when the observable shortening of objects moving at speeds approaching the
speed of light.
- Objects are measured to be shorter in the direction that they are moving with respect
to a stationary observer.
Ex: How is it possible that the two observers measure the same rocket ship to be two
different lengths? When the rocket ship is at rest on the earth, the on-ship meter stick
and the off-ship meter stick are exactly the same but when the rocket ship flies past the
earth at significant fraction of the speed of light, the on-ship meter stick as seen by the
on earth observer has shrunk. When the observer on ship says the ship is still 15 m
long, the observer on earth says, "Nope, your meter stick has shrunk and so has your
ship. The ship now measures 7.5 m long using my meter stick." The on-ship meter stick
shrinks by the same percentage that the ship shrinks.
E=mc^2 - answerEnergy and mass are equivalent and transmutable. (Mass-energy
equivalence).
No physical object can travel faster
than___________________________________________. - answerthe speed of light in
a vacuum. (Maximum speed is finite).
Postulate 2 - answerAccording to this postulate, the speed of the light as observed
inside the space ship by that observer must be 3×10^8 m/s and the speed of light
observed by the observer on the earth (the light moving diagonally) must ALSO be
3×10^8 m/s.
Twin Paradox - answerShortly after Einstein proposed the special theory of relativity, an
apparent paradox was pointed out. This paradox involved a pair of twins, one of whom
traveled away from the earth and returned at very high speeds. The other twin remained
at home on earth. Since one twin was traveling at very high speed, time for him was
running slower than for the twin who remained on earth. Thus the traveling twin would
return home younger than the twin who remained on earth.
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