Question 1

Your spaceship is passing your friend's ship,which is traveling in the opposite direction.You measure his ship to be moving at 60% of the speed of light relative to you.Later you ask your friend what he measured your speed to be at that time relative to him.What is his answer?

Accepted Answer

The answer of Your spaceship is passing your friend's ship,which...

Question 2

A clock is moving across your line of sight with its face turned toward you.Which statement about this clock,as seen by you,is NOT correct?

Accepted Answer

The answer of A clock is moving across your line...

Question 3

A clock with a luminous dial is moving toward you at a speed that is a large fraction of the speed of light.What will you observe?

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The answer of A clock with a luminous dial is...

Question 4

Suppose you are in a spaceship traveling toward Earth at 95% of the speed of light.Compared with when your ship was at rest on Mars,what length do you measure for your spaceship?

Accepted Answer

According to the theory of relativity, the length of an object in its own rest frame remains the same. Since you are measuring the length of the spaceship from within it, it remains unchanged.

Question 5

Suppose you are in a jet airliner traveling at a constant speed of 400 km/h in a constant direction.All windows are blocked,so you cannot see outside,and there are no vibrations from the engines.What experiment can you do to determine that you are in fact moving?

Accepted Answer

In a situation where you are moving at a constant speed and direction, without external references or forces, all experiments will yield the same results as if you were at rest due to the principle of relativity.

Question 6

Suppose you see a spaceship with a clock on it hurtling past you at 80% of the speed of light.As it goes by,the second hand on the ship's clock ticks off five seconds.How much time elapsed on your clock during this occurrence?

Accepted Answer

According to special relativity, time is relative to the observer's frame of reference. In this case, the spaceship is moving at 80% of the speed of light relative to the observer. This means that time on the spaceship will appear to be slower to the observer than time on their own clock. This phenomenon is known as time dilation. As a result, more than 5 seconds would have elapsed on the observer's clock during the 5 seconds observed on the spaceship's clock. The exact amount of time elapsed can be calculated using the time dilation equation: 
t' = t / sqrt(1 - v^2/c^2)
where t' is the time elapsed on the observer's clock, t is the time elapsed on the spaceship's clock, v is the velocity of the spaceship, and c is the speed of light. Plugging in the given values:
t' = 5 / sqrt(1 - 0.8^2) 
t' = 8.66 seconds (approximately) 
Therefore, the correct choice is C) more than 5 seconds.

Question 7

Which is a CORRECT and complete statement of Einstein's first postulate of special relativity?

Accepted Answer

Einstein's first postulate of special relativity states that the laws of physics are the same in all inertial frames of reference, meaning they are the same regardless of the constant velocity at which you move.

Question 8

Two spaceships are traveling past Earth at 90% of the speed of light in opposite directions (i.e.,they are approaching each other).One turns on a searchlight,which is seen by scientists aboard the other.What speed do the scientists measure for this light (c = speed of light in a vacuum)?

Accepted Answer

According to the principle of relativity, the speed of light in a vacuum is always measured as c, regardless of the relative speeds of the observer and the source of light. Therefore, the scientists aboard the other spaceship will measure the speed of the searchlight as c, even though the spaceship emitting the light is traveling at 90% of the speed of light in the opposite direction.

Question 9

In which "frame of reference" would matter behave exactly as it would in a stationary frame of reference?

Accepted Answer

In a stationary frame of reference, matter behaves according to the laws of physics that are applicable at rest. In order for matter to behave exactly as it would in a stationary frame of reference, the frame of reference must also be at rest or moving at a constant velocity. Option C describes a frame of reference that is moving at a constant velocity, which means that matter in this frame of reference would behave the same as it would in a stationary frame of reference. Options A, B, and D describe frames of reference that are accelerating or moving in a curved path, which would result in different physical behavior of matter compared to a stationary frame of reference.

Question 10

A child on a playground swing is swinging back and forth (one complete oscillation)once every 4 seconds,as seen by her father standing next to the swing.At the same time,a spaceship is hurtling by at a speed close to the speed of light.According to special relativity (and ignoring the Doppler effect for this question),her mother on the spaceship finds that the time for one full swing is:

Accepted Answer

According to special relativity, time appears to slow down for an object in motion relative to an observer. Therefore, the mother on the spaceship would observe that the swing is moving slower than the father on the ground does. This means that the period (time for one full swing) appears longer to her. Therefore, the time for one full swing would be more than 4 seconds.

Question 11

If you stay on Earth while a friend races off in a rocket at close to the speed of light,then,according to special relativity,you will see a clock on the rocket appear to tick more slowly than the one on your wall.If your friend looks back at your clock,then,according to the same theory,the friend will see your clock appear to tick:

Accepted Answer

According to special relativity, time dilation occurs for moving objects. An observer in a moving frame of reference will see clocks in a stationary frame of reference ticking slower than clocks in their own frame of reference. This is a reciprocal effect, so the friend in the rocket will also see the clock on Earth ticking slower than the clock on the rocket.

Question 12

In a TV tube,the picture is created by a beam of electrons that travels down the tube at a very high speed.What is the mass of one of these electrons,compared with an electron at rest?

Accepted Answer

The mass of a moving electron appears to increase due to relativistic effects as its speed approaches the speed of light.

Question 13

How must an object be moving for us to be able to use the theory of special relativity to describe the object?

Accepted Answer

Special relativity applies to objects moving at a constant speed in a straight line, regardless of how fast they are moving.

Question 14

Suppose you are in the Space Shuttle in orbit around Earth at a speed of 7 km/s,and at some particular time your direction of travel is straight toward the Sun.The speed of light in a vacuum is 300,000 km/s.What speed will you measure for light from the Sun?

Accepted Answer

According to the principle of special relativity, the speed of light is constant and independent of the speed of the observer. Therefore, no matter what the speed of the Space Shuttle is, the measured speed of light will always be 300,000 km/s. The option A and B are incorrect because the speed of the observer does not affect the speed of light. Option C is incorrect because relativistic contraction affects the length of objects in the direction of motion, but it has no effect on the speed of light.

Question 15

You are on Mars standing on the gangplank of your spaceship when you see an identical spaceship go past Mars at 90% of the speed of light.When you look closely at this spaceship,how does it compare with your own spaceship?

Accepted Answer

According to the theory of relativity, objects moving at high speeds appear contracted in the direction of motion (length contraction) and time on them appears to move more slowly (time dilation) compared to a stationary observer.

Question 16

Fred and Joanne both measure the length of a particular spaceship to be 100 m when it is on Earth.Joanne then gets into the spaceship and,after visiting the Moon,hurtles past Earth at a speed close to the speed of light.Fred,still on Earth,measures the length of the moving spaceship to be about 90 m.At the same time,Joanne (using her own meterstick)measures the length of the spaceship to be:

Accepted Answer

According to the theory of relativity, as an object's speed approaches the speed of light, its length appears to shrink from the point of view of a stationary observer. This effect is known as length contraction. Therefore, Fred observes the spaceship to be shorter than it actually is due to Joanne's high speed. However, from Joanne's point of view on the spaceship, she is at rest and the spaceship appears to be its original length of 100 m. Therefore, the correct answer is B, Joanne measures the length of the spaceship to be 100 m because she is "at rest" on the spaceship.

Question 17

If you see an object moving past you at 90% of the speed of light,what will its length appear to be?

Accepted Answer

According to the theory of relativity, as an object approaches the speed of light, its length will appear to shorten in the direction of motion. This is known as length contraction. Therefore, if an object is moving past us at 90% of the speed of light, it will appear shorter than if it were at rest.

Question 18

Why does Einstein's theory of special relativity carry the name special?

Accepted Answer

Einstein's theory of special relativity is termed "special" because it applies to the specific case of objects moving at a constant speed in a straight line, excluding scenarios involving acceleration or gravity, which are addressed by the theory of general relativity.

Question 19

Suppose you are aboard a spaceship that is passing Earth at 80% of the speed of light.You see a clock on Earth tick off 5 seconds.How much time elapses on your own clock while this is happening?

Accepted Answer

The answer of Suppose you are aboard a spaceship that...

Question 20

Which statement is NOT a consequence of the postulates of special relativity?

Accepted Answer

The answer of Which statement is NOT a consequence of...

Quiz 12: The Deaths and Remnants of Stars