Question 1

Consider a spaceship that moves toward you at half the speed of light.It fires a probe toward you,relative to itself,at 0.7 the speed of light.Relative to you,the probe approaches at about

Accepted Answer

The relativistic velocity addition formula is used here: v = (v1 + v2) / (1 + v1*v2/c^2). Plugging in v1 = 0.5c and v2 = 0.7c, we get v ≈ 0.89c.

Question 2

Consider a spaceship that moves away from you at half the speed of light.It fires a probe,also away from you,at half the speed of light relative to the spaceship.Relative to you,the probe moves at

Accepted Answer

The answer of Consider a spaceship that moves away from...

Question 3

Suppose two spaceships approach each other at the speed of light,and each sends a beam of light to warn the other of its approach.From the frame of reference of either spaceship,the light will reach the other ship

Accepted Answer

According to the theory of relativity, as the spaceships approach each other at the speed of light, time dilation occurs, and the distance between them appears to shrink from the perspective of both ships. Therefore, the light beams sent by each spaceship will reach the other ship before they actually collide. This is because the speed of light is constant in all frames of reference, and it cannot be exceeded by any object or event.

Question 4

If you use the relativistic velocity-addition formula to add everyday velocities,you will get

Accepted Answer

The relativistic velocity-addition formula reduces to the classical formula at low velocities. Therefore, adding everyday velocities using the relativistic formula will result in a result almost identical to the classical result. The choice A is incorrect because the relativistic formula is a well-established equation in physics and does not produce nonsensical results. The choice B is incorrect because while the relativistic formula does give a more accurate result than the classical formula at high velocities, the difference is negligible for everyday velocities.

Question 5

If a 1-microgram antimatter meteor were to strike the Earth,the amount of energy of forms other than mass that would be produced would be

Accepted Answer

Using Einstein's famous equation E=mc^2, where E is energy, m is mass, and c is the speed of light, we can calculate the amount of energy released if the 1-microgram antimatter meteor were to annihilate with an equal mass of matter on Earth. 
The total mass that would be annihilated is (1μg + 1μg) = 2μg. 
The energy released would be E = (2μg) x (3 x 10^8 m/s)^2 = 1.8 x 10^14 joules.
However, the question asks specifically for the amount of energy of forms other than mass that would be produced. Since all of the mass of the antimatter meteor would be converted into energy, the full 1.8 x 10^14 joules would be in the form of non-mass energy. 
Therefore, the answer is E) 180 billion joules.

Question 6

There is an upper limit on the speed of a particle.This means there is also an upper limit on its

Accepted Answer

The answer of There is an upper limit on the...

Question 7

A heavy meterstick has a mass of 1 kg.When the meterstick is thrown like a spear past you,you measure its momentum to be 2mv.What do you measure its length to be?

Accepted Answer

The answer of A heavy meterstick has a mass of...

Question 8

Suppose a blinking light source uniformly accelerates away from you.As the source gets farther and farther away,you'll notice that the frequency of the flashes

Accepted Answer

This phenomenon is known as the Doppler effect. In this case, the light source is moving away from the observer, which causes the wavelength of the light to appear longer, thus decreasing its frequency. This effect is commonly observed in everyday life, such as the noticeable change in pitch of sirens from an ambulance or police car as it passes by.

Question 9

A 10-meter-long spear is thrown at relativistic speeds through a 10-meter-long pipe.(Both these dimensions are measured when each is at rest. )When the spear passes through the pipe,which of the following statements is true?

Accepted Answer

The observed length contraction depends on the observer's frame of reference. To an observer at rest with the pipe, the spear appears contracted and fits inside. To an observer moving with the spear, the pipe appears contracted, and the spear extends from both ends.

Question 10

Radioactive muons formed high in the atmosphere have an average lifetime of 2 millionths of a second and travel toward Earth at nearly the speed of light.They are so high they should have decayed by the time they reach the Earth's surface,according to pre-relativity physics.They don't because they

Accepted Answer

Both time dilation and length contraction are effects of special relativity that allow muons to reach the Earth's surface. Time dilation means they experience a longer lifetime in the Earth's frame, and length contraction means the distance they travel is shorter in their own frame.

Quiz 35: Special Theory of Relativity