Question 1

How does the attractive force you feel compare if you are just outside the event horizon of a massive black hole or of a relatively small black hole?

Accepted Answer

A) Because of its larger mass, the massive black hole will exert the larger force. 
B) As the mass of the black hole increases, the Schwarzschild radius increases linearly but the gravitational attraction decreases as 1/r2. Thus, the larger black hole exerts the smaller force. 
C) As the mass of the black hole increases, the Schwarzschild radius increases linearly but the gravitational attraction decreases as 1/r2. Thus, the larger black hole exerts the larger force. 
D) All black holes exert a large but equal force on an object just outside the event horizon.

Question 2

In the event observed by LIGO on September 14, 2015, two black holes with a combined mass of 65 Mε merged to form a black hole with 63 Mε. What happened to the difference in mass?

Accepted Answer

A) It was converted almost instantly into gravitational wave energy. 
B) It was converted into smaller particles like neutrinos. 
C) It formed an accretion disk around the merged black hole. 
D) It was converted into different wavelengths of visible light.

Question 3

In what way is the general theory of relativity more general (deals with more situations) than the special theory?

Accepted Answer

A) It includes accelerated motion but not gravitation. 
B) It includes accelerated motion and gravitation. 
C) It includes only constant, unaccelerated motion. 
D) It includes only motion at the speed of light.

Question 4

The discovery of the Crab Pulsar, with a period of only 1/30 s, ruled out a number of possible explanations for pulsars. These included all of the following EXCEPT ONE. Which one was the exception?

Accepted Answer

A) eclipsing binaries 
B) rapidly shifting dark dust clouds 
C) variable stars 
D) rotating white dwarfs

Question 5

Why is the orbit of Mercury important from the standpoint of general relativity?

Accepted Answer

A) General relativity predicts that Mercury should move more slowly in its orbit than it does. 
B) General relativity predicts the correct value for the advance of the perihelion of Mercury's orbit while Newtonian mechanics does not. 
C) General relativity predicts the correct speed for Mercury in its orbit while Newtonian mechanics does not. 
D) The inability to predict the advance of the perihelion of the orbit of Mercury is a significant failure for general relativity.

Question 6

How does a gravitational field affect the passage of time?

Accepted Answer

A) Gravity has no effect on the passage of time. 
B) Clocks in a gravitational field run faster than clocks outside the field. 
C) Gravity makes time stop. 
D) Clocks in a gravitational field run slower than clocks outside the field.

Question 7

It is theoretically possible for a rotating black hole to transfer energy to the accretion disk surrounding it. The mechanism through which the energy is transferred is:

Accepted Answer

A) the magnetic field of the black hole. 
B) the magnetic field of the accretion disk. 
C) electromagnetic radiation passing out of the black hole. 
D) neutral particles passing out of the black hole.

Question 8

If the Schwarzschild radius of a 2-Mε black hole is 6 km, what is it for a 5-Mε black hole?

Accepted Answer

A) 150 km 
B) 15 m 
C) 15,000 km 
D) 15 km

Question 9

A typical galaxy has a mass of 1011 Mε. If 1% of this mass collects at the center of the galaxy to become a nonrotating black hole, what will be its Schwarzschild radius?

Accepted Answer

A) 20 au 
B) 20,000 au 
C) 20 ly 
D) 20 pc

Question 10

Tidal forces distort objects near black holes. These tidal forces:

Accepted Answer

A) are more severe for more massive black holes. 
B) are more severe for less massive black holes. 
C) are equally severe for all black holes independent of mass. 
D) exist only for Kerr (rotating) black holes.

Question 11

The escape velocity of matter from the center of a black hole whose mass is 3 Mε is:

Accepted Answer

A) quite small. 
B) greater than the speed of light. 
C) exactly equal to the speed of light. 
D) about half the speed of light.

Question 12

What is the Schwarzschild radius of a black hole that is 2 Mε?

Accepted Answer

A) 6000 km 
B) 6.0 m 
C) 60 km 
D) 6.0 km

Question 13

All black hole candidates observed so far are:

Accepted Answer

A) eclipsing binaries in which the light is totally extinguished periodically. 
B) dark areas surrounded by light from background stars. 
C) x-ray sources in spectroscopic binary systems. 
D) "attractors" toward which objects within a large volume of space are accelerating.

Question 14

What is believed to be the maximum mass for a neutron star?

Accepted Answer

A) 150 Mε 
B) 12 Mε 
C) 3 Mε 
D) 1.4 Mε

Question 15

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million Mε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission)?

Accepted Answer

A) 2.6 million K 
B) This would be the surface temperature of 2.6 million neutron stars joined together, at least 106 K. 
C) Black holes emit gamma rays with wavelengths around 10-12 m. Wien's law then gives a temperature of around 2 × 109 K. 
D) essentially, absolute zero

Question 16

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 1010 kg. What is the Schwarzschild radius of such a black hole?

Accepted Answer

A) 5.0 × 10-21 m 
B) 1.5 × 10-17 m 
C) 6.3 × 10-4 m 
D) 1.5 au

Question 17

The escape speed from a neutron star is:

Accepted Answer

A) less than the speed of light. 
B) equal to the speed of light. 
C) greater than the speed of light. 
D) independent of the mass of the neutron star.

Question 18

In the Penrose process it is theoretically possible to:

Accepted Answer

A) travel through the center of a black hole and emerge again. 
B) extract energy from a black hole. 
C) extract energy from the accretion disk around a black hole. 
D) travel for a short distance inside the event horizon and emerge again.

Question 19

Take two identical, nonrotating, 5-M? black holes and place them side by side. Add 1 M? of pineapples to the left-hand one and 1 M ? of radioactive uranium to the right-hand one (without changing their electric charge or their rotation). Afterward, how do these two black holes differ?

Accepted Answer

A) The left-hand one will smell better. 
B) The right-hand one is radioactive, emitting alpha particles, electrons, and gamma rays. 
C) The right-hand one has a stronger gravitational field because of the denser matter inside it. 
D) They do not differ at all.

Question 20

How do rotating black holes differ from nonrotating black holes?

Accepted Answer

A) Rotating black holes have a region just inside the event horizon in which nothing can be at rest. 
B) Rotating black holes have a region just outside the event horizon in which nothing can be at rest. 
C) Rotating black holes have a magnetic field due to the spin of electrically charged matter. 
D) Not at all; the only property that distinguishes one black hole from another is mass, not spin.

Exam 21: Stellar Remnants: Neutron Stars and Black Holes

How does the attractive force you feel compare if you are just outside the event horizon of a massive black hole or of a relatively small black hole?

In the event observed by LIGO on September 14, 2015, two black holes with a combined mass of 65 M_ε merged to form a black hole with 63 M_ε. What happened to the difference in mass?

In what way is the general theory of relativity more general (deals with more situations) than the special theory?

The discovery of the Crab Pulsar, with a period of only 1/30 s, ruled out a number of possible explanations for pulsars. These included all of the following EXCEPT ONE. Which one was the exception?

Why is the orbit of Mercury important from the standpoint of general relativity?

How does a gravitational field affect the passage of time?

It is theoretically possible for a rotating black hole to transfer energy to the accretion disk surrounding it. The mechanism through which the energy is transferred is:

If the Schwarzschild radius of a 2-M_ε black hole is 6 km, what is it for a 5-M_ε black hole?

A typical galaxy has a mass of 10¹¹ M_ε. If 1% of this mass collects at the center of the galaxy to become a nonrotating black hole, what will be its Schwarzschild radius?

Tidal forces distort objects near black holes. These tidal forces:

The escape velocity of matter from the center of a black hole whose mass is 3 M_ε is:

What is the Schwarzschild radius of a black hole that is 2 M_ε?

All black hole candidates observed so far are:

What is believed to be the maximum mass for a neutron star?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million M_ε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 10¹⁰ kg. What is the Schwarzschild radius of such a black hole?

The escape speed from a neutron star is:

In the Penrose process it is theoretically possible to:

Take two identical, nonrotating, 5-M_? black holes and place them side by side. Add 1 M_? of pineapples to the left-hand one and 1 M ? of radioactive uranium to the right-hand one (without changing their electric charge or their rotation) . Afterward, how do these two black holes differ?

How do rotating black holes differ from nonrotating black holes?

Exam 21: Stellar Remnants: Neutron Stars and Black Holes

How does the attractive force you feel compare if you are just outside the event horizon of a massive black hole or of a relatively small black hole?

In the event observed by LIGO on September 14, 2015, two black holes with a combined mass of 65 Mε merged to form a black hole with 63 Mε. What happened to the difference in mass?

In what way is the general theory of relativity more general (deals with more situations) than the special theory?

The discovery of the Crab Pulsar, with a period of only 1/30 s, ruled out a number of possible explanations for pulsars. These included all of the following EXCEPT ONE. Which one was the exception?

Why is the orbit of Mercury important from the standpoint of general relativity?

How does a gravitational field affect the passage of time?

It is theoretically possible for a rotating black hole to transfer energy to the accretion disk surrounding it. The mechanism through which the energy is transferred is:

If the Schwarzschild radius of a 2-Mε black hole is 6 km, what is it for a 5-Mε black hole?

A typical galaxy has a mass of 1011 Mε. If 1% of this mass collects at the center of the galaxy to become a nonrotating black hole, what will be its Schwarzschild radius?

Tidal forces distort objects near black holes. These tidal forces:

The escape velocity of matter from the center of a black hole whose mass is 3 Mε is:

What is the Schwarzschild radius of a black hole that is 2 Mε?

All black hole candidates observed so far are:

What is believed to be the maximum mass for a neutron star?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million Mε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 1010 kg. What is the Schwarzschild radius of such a black hole?

The escape speed from a neutron star is:

In the Penrose process it is theoretically possible to:

Take two identical, nonrotating, 5-M? black holes and place them side by side. Add 1 M? of pineapples to the left-hand one and 1 M ? of radioactive uranium to the right-hand one (without changing their electric charge or their rotation) . Afterward, how do these two black holes differ?

How do rotating black holes differ from nonrotating black holes?

In the event observed by LIGO on September 14, 2015, two black holes with a combined mass of 65 M_ε merged to form a black hole with 63 M_ε. What happened to the difference in mass?

If the Schwarzschild radius of a 2-M_ε black hole is 6 km, what is it for a 5-M_ε black hole?

A typical galaxy has a mass of 10¹¹ M_ε. If 1% of this mass collects at the center of the galaxy to become a nonrotating black hole, what will be its Schwarzschild radius?

The escape velocity of matter from the center of a black hole whose mass is 3 M_ε is:

What is the Schwarzschild radius of a black hole that is 2 M_ε?

The black hole at the center of the Milky Way Galaxy is estimated to have a mass of roughly 4 million M_ε. What is the TEMPERATURE of this black hole (that is, the temperature of a blackbody with an equivalent energy emission) ?

The age of the universe is roughly 14 billion years, which is also the approximate evaporation time for a black hole with a mass of 10¹⁰ kg. What is the Schwarzschild radius of such a black hole?

Take two identical, nonrotating, 5-M_? black holes and place them side by side. Add 1 M_? of pineapples to the left-hand one and 1 M ? of radioactive uranium to the right-hand one (without changing their electric charge or their rotation) . Afterward, how do these two black holes differ?