Question 1

Explain why no object that has mass can ever move at a speed equal to the speed of light.At what velocity do massless particles (e.g. ,photons)travel in vacuum?

Accepted Answer

According to relativity,increasing the s

Question 2

As shown in this figure,an observer in a windowless room notices that light from a flashlight does not follow a straight path,but instead seems to be bent downwards as it crosses the room.What does the observer conclude is happening?

Accepted Answer

A) The room is experiencing an acceleration from gravity. 
B) The room is accelerating upward. 
C) Both A and B at the same time. 
D) Either A or B;it is impossible to tell the difference. 
E) Either A or B,depending on whether massive objects in the room fall downward or float upward when released. 
A) The room is experiencing an acceleration from gravity. 
B) The room is accelerating upward. 
C) Both A and B at the same time. 
D) Either A or B;it is impossible to tell the difference. 
E) Either A or B,depending on whether massive objects in the room fall downward or float upward when released.

Question 3

Which of the following is a consequence of Einstein's special theory of relativity?

Accepted Answer

A) Moving clocks run quicker. 
B) The velocity of light depends on the speed of the observer. 
C) Distances are shorter for objects traveling close to the speed of light. 
D) Gravity arises because mass distorts spacetime. 
E) Faster moving objects require less force to accelerate them. 
A) Moving clocks run quicker. 
B) The velocity of light depends on the speed of the observer. 
C) Distances are shorter for objects traveling close to the speed of light. 
D) Gravity arises because mass distorts spacetime. 
E) Faster moving objects require less force to accelerate them.

Question 4

If the Sun suddenly turned into a black hole,what would be the radius of its event horizon?

Accepted Answer

A) 3 m 
B) 30 m 
C) 300 m 
D) 3 km 
E) 30 km 
A) 3 m 
B) 30 m 
C) 300 m 
D) 3 km 
E) 30 km

Question 5

Describe two early verifications of the prediction of relativity.

Accepted Answer

In 1919,Eddington measured the gravitati

Question 6

The aberration of starlight is:

Accepted Answer

A) a change in the wavelength of light caused by the motion of the light source 
B) poor focusing of starlight caused by imperfections in the optics of a telescope 
C) a change in the direction of starlight caused by its passage through the earth's atmosphere 
D) an increase in the wavelength of light as it leaves the surface of a gravitating body 
E) a change in the direction of starlight caused by the orbital motion of the Earth 
A) a change in the wavelength of light caused by the motion of the light source 
B) poor focusing of starlight caused by imperfections in the optics of a telescope 
C) a change in the direction of starlight caused by its passage through the earth's atmosphere 
D) an increase in the wavelength of light as it leaves the surface of a gravitating body 
E) a change in the direction of starlight caused by the orbital motion of the Earth

Question 7

Gravity is nothing more than a curvature in the fabric of spacetime.

Accepted Answer

A) True 
 B)False

Question 8

Gravitational lensing allows us to see distant objects brightened and distorted because of massive objects in the path that the light from the object travels.

Accepted Answer

A) True 
 B)False

Question 9

Why do astronauts in space feel no gravity?

Accepted Answer

A) There is no gravity out in space. 
B) Gravity only happens when objects are accelerating. 
C) In space,the gravity from the Moon and the Sun cancels out the Earth's gravity. 
D) They and their spaceship are both freely falling at the same rate in the gravitational field. 
E) The astronauts do not have any mass when they are out in space. 
A) There is no gravity out in space. 
B) Gravity only happens when objects are accelerating. 
C) In space,the gravity from the Moon and the Sun cancels out the Earth's gravity. 
D) They and their spaceship are both freely falling at the same rate in the gravitational field. 
E) The astronauts do not have any mass when they are out in space.

Question 10

Explain what four-dimensional spacetime means.

Accepted Answer

In relativity,space and time have to be

Question 11

You measure that an object has a mass of exactly 1 kg by weighing it in the Earth's gravitational field.The equivalence principle says that the mass you would measure by trying to accelerate it would be:

Accepted Answer

A) 1 kg 
B) greater than 1 kg 
C) less than 1 kg 
D) different from 1kg,depending on what it's made of 
E) larger than 1 kg because of the Sun's gravity 
A) 1 kg 
B) greater than 1 kg 
C) less than 1 kg 
D) different from 1kg,depending on what it's made of 
E) larger than 1 kg because of the Sun's gravity

Question 12

The twin paradox shows that special relativity:

Accepted Answer

A) explains many things but can't explain everything 
B) is accurate but contains some worrisome contradictions 
C) is incorrect 
D) only explains things in steady motion,but cannot be used to explain objects that accelerate 
E) correctly accounts for the results of experiments in different reference frames 
A) explains many things but can't explain everything 
B) is accurate but contains some worrisome contradictions 
C) is incorrect 
D) only explains things in steady motion,but cannot be used to explain objects that accelerate 
E) correctly accounts for the results of experiments in different reference frames

Question 13

How would the Newtonian theory explain the orbit of the Earth around the Sun? What would the explanation be in general relativity?

Accepted Answer

In Newton's theory of gravity,the Sun an

Question 14

The bending of light passing near a massive object is called:

Accepted Answer

A) time dilation 
B) the twin paradox 
C) gravitational lensing 
D) length contraction 
E) mass increase 
A) time dilation 
B) the twin paradox 
C) gravitational lensing 
D) length contraction 
E) mass increase

Question 15

One result of relativity is that an astronaut in a windowless spacecraft could tell the difference between falling freely and the presence of a nearby gravitational source.

Accepted Answer

A) True 
 B)False

Question 16

How does relativity compare to Newtonian physics?

Accepted Answer

A) Relativity gives the same result as Newtonian physics when objects are moving slowly. 
B) Relativity gives results that contradict many predictions of Newtonian physics,so we know the latter is incorrect. 
C) Relativity must be better because it is a newer theory than Newtonian physics. 
D) Newtonian physics and relativity make the same predictions,but it's easier to compute results using relativity. 
E) Newtonian physics makes predictions that are at odds with certain observations,whereas relativity is consistent with those observations. 
A) Relativity gives the same result as Newtonian physics when objects are moving slowly. 
B) Relativity gives results that contradict many predictions of Newtonian physics,so we know the latter is incorrect. 
C) Relativity must be better because it is a newer theory than Newtonian physics. 
D) Newtonian physics and relativity make the same predictions,but it's easier to compute results using relativity. 
E) Newtonian physics makes predictions that are at odds with certain observations,whereas relativity is consistent with those observations.

Question 17

What does gravity mean in relativity?

Accepted Answer

A) It is a result of mass and energy being two forms of the same thing. 
B) It is a consequence of distances getting shorter as objects move faster. 
C) It is the result of the mass of falling bodies getting bigger because they are in motion. 
D) It is the force that objects with mass exert on a body. 
E) It is the result of the distortion in spacetime around an object with any energy density. 
A) It is a result of mass and energy being two forms of the same thing. 
B) It is a consequence of distances getting shorter as objects move faster. 
C) It is the result of the mass of falling bodies getting bigger because they are in motion. 
D) It is the force that objects with mass exert on a body. 
E) It is the result of the distortion in spacetime around an object with any energy density.

Question 18

Most black holes are found:

Accepted Answer

A) by the watching the orbits of nearby stars 
B) from the bending of the light from background stars 
C) by finding objects that emit no light 
D) by the X-rays produced by a surrounding accretion disk 
E) by the detection of Hawking radiation 
A) by the watching the orbits of nearby stars 
B) from the bending of the light from background stars 
C) by finding objects that emit no light 
D) by the X-rays produced by a surrounding accretion disk 
E) by the detection of Hawking radiation

Question 19

According to relativity,spacecraft that can travel faster than the speed of light are:

Accepted Answer

A) impossible,because nothing can travel that fast 
B) possible,but not useful since they could not contain living beings 
C) impossible,since objects that travel that fast would get shorter and squeeze out space for the astronauts to live 
D) possible,if we are clever enough with new technologies 
E) impossible,because they would require new energy sources that are not yet invented 
A) impossible,because nothing can travel that fast 
B) possible,but not useful since they could not contain living beings 
C) impossible,since objects that travel that fast would get shorter and squeeze out space for the astronauts to live 
D) possible,if we are clever enough with new technologies 
E) impossible,because they would require new energy sources that are not yet invented

Question 20

What is true about muons?

Accepted Answer

A) They are always moving at high speed,so they test relativity. 
B) Relativity explains why we can see short-lived muons that are produced high in the atmosphere from cosmic rays. 
C) We can see them being deflected from straight lines by the gravity of black holes. 
D) They have a mass that does not increase if they are moving fast. 
E) They are examples of Hawking radiation from black holes. 
A) They are always moving at high speed,so they test relativity. 
B) Relativity explains why we can see short-lived muons that are produced high in the atmosphere from cosmic rays. 
C) We can see them being deflected from straight lines by the gravity of black holes. 
D) They have a mass that does not increase if they are moving fast. 
E) They are examples of Hawking radiation from black holes.

Exam 18: Relativity and Black Holes

Explain why no object that has mass can ever move at a speed equal to the speed of light.At what velocity do massless particles (e.g. ,photons)travel in vacuum?

As shown in this figure,an observer in a windowless room notices that light from a flashlight does not follow a straight path,but instead seems to be bent downwards as it crosses the room.What does the observer conclude is happening?

Which of the following is a consequence of Einstein's special theory of relativity?

If the Sun suddenly turned into a black hole,what would be the radius of its event horizon?

Describe two early verifications of the prediction of relativity.

The aberration of starlight is:

Gravity is nothing more than a curvature in the fabric of spacetime.

Gravitational lensing allows us to see distant objects brightened and distorted because of massive objects in the path that the light from the object travels.

Why do astronauts in space feel no gravity?

Explain what four-dimensional spacetime means.

You measure that an object has a mass of exactly 1 kg by weighing it in the Earth's gravitational field.The equivalence principle says that the mass you would measure by trying to accelerate it would be:

The twin paradox shows that special relativity:

How would the Newtonian theory explain the orbit of the Earth around the Sun? What would the explanation be in general relativity?

The bending of light passing near a massive object is called:

One result of relativity is that an astronaut in a windowless spacecraft could tell the difference between falling freely and the presence of a nearby gravitational source.

How does relativity compare to Newtonian physics?

What does gravity mean in relativity?

Most black holes are found:

According to relativity,spacecraft that can travel faster than the speed of light are:

What is true about muons?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornments Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

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