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PHY S 100 > Units 7-8 > Flashcards

Units 7-8 Flashcards

1
Q

How do we best test a law of nature?

A

By examining it under extreme conditions

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2
Q

What does the letter “c” denote?

A

The speed of light traveling through empty space, the absolute limit of speed.

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3
Q

What does c equal?

A

3 x 10^8 m/sec of 6.7 x 10^8 mph

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4
Q

What particles reach speeds close to that of light?

A

Cosmic rays - atomic sized particles coming from outer space

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5
Q

True or False: Newton’s law of motion apply to things traveling at average speeds and those traveling at the speed of light.

A

FALSE.
Shockingly.

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6
Q

What law modifies Newton’s laws of motion?

A

Special theory of relativity

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7
Q

True or False: Starting in chapter 7, a person standing on earth is motionless.

A

False
They are standing on the earth which has motion.

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8
Q

True or False: The speed of light is inhibited by air molecules, and thus only reaches its true potential for speed in a vacuum.

A

True

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9
Q

True or False: Newton’s first theory involved God being at the center of the universe in a place of eternal rest, where nothing moved.

A

True

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10
Q

True or False: Motion is always and only measured with respect to “reference frames,” like the surface of the Earth or the Sun which have their own states of motion.

A

True

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11
Q

Why is absolute motion impossible?

A

Because we can only measure motion by comparing it to something else, and all things we know of move in some capacity.

Absolute motion could only exist if we could compare the motion of something to a thing that was eternally at rest and never moving (outside of the force).

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12
Q

What is the idea of relativity? Or relative motion?

A

The idea that motion is only determined with respect to other objects (which have their own motion) and therefore has no absolute value

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13
Q

What is the inertial frame of reference?

A

A state of motion that is experiencing no acceleration.
Uniform motion
1st law

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14
Q

What is a non-inertial frame of reference?

A

A state of motion that is undergoing acceleration.
2nd law

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15
Q

What is motion symmetry?

A

The laws of nature remain the same for all observers in inertial frames of reference.

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16
Q

True or False: Motion symmetry applies to non-inertial frames of reference

A

FALSE

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17
Q

What is the science that studies non-inertial frames of reference?

A

General theory of relativity

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18
Q

True or False: Velocity can have different values depending on how we choose to measure it.

A

True

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19
Q

What is Galilean relativity?

A

The idea that a final speed vector can be computed by directly adding all individual velocity vectors together according to the rules of Euclidean geometry.

In other words, you compare all the vectors (arrows that indicate speed and direction) of all the motions on an object relative to its surroundings, and do math to calculate ONE SINGLE speed.

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20
Q

True or False: Light obeys Galilean relativity

A

FALSE
WOAH
Regardless of what is happening around it, the speed of light is always the same.

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21
Q

What are the two explanations of why light does not obey the Galilean relativity?

A
  1. Nature has special rules for adding the velocity of light to other velocities.
  2. Light DOES follow the same rules, we are just not using the proper rules!
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22
Q

What are the two assumptions of the special theory of relativity?

A
  1. The laws of nature are the same for all observers in inertial frames of reference (i.e. the principle of motion symmetry)
  2. The speed of light in a vacuum has a constant value, regardless of the speed of the device emitting the light or the speed of the observer receiving the light.
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23
Q

What idea was Einstein famous for introducing to the scientific community?

A

Not only is there no absolute motion, there is also no absolute space or time

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24
Q

What does Gedanken mean?

A

Thought

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25
Q

True or False: Simultaneity is relative

A

True
Think of the Jane and Tom lighting experiment. Neither were wrong and both were right.

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26
Q

What did the Jane and Tom lightning Gedanken suggest?

A

That observers moving relative to each other will experience the same events at different times.

There is an ACTUAL DIFFERENCE in when events occur in time :O It is not psychological or magic. It is REAL.

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27
Q

Time dilation

A

The slowing of a clock as its speed approaches the speed of light, measured by an observer not moving with the clock.

In other words, moving clocks run slower than stationary clocks. (or moving time)

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28
Q

True or False: Time dilation is an illusion

A

FALSE
It is real and testable

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29
Q

How would you summarize time dilation?

A

Something in motion is passing time SLOWER than a standard time clock.

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30
Q

What is length contraction?

A

When we measure the lengths of objects moving PAST us, we find their lengths to be shorter in the direction of their motion than if we measured their lengths while traveling WITH them.
Again, very real.

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31
Q

What is spacetime?

A

Space and time connected together into one continuum by the special theory of relativity.

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32
Q

True or False: Time and space depend on speed

A

TRUE

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33
Q

Who came up with the space-time concept?

A

Minkowski, Einstein’s teacher

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34
Q

True or False: Faster speeds can be thought of as causing a rotation in space-time

A

Trueish

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35
Q

What is the spacetime equation?

A

l^2 - (ct)^2 = s^2

l = spatial separation
t = time between two events
c = speed of light
s = length of a line segment

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36
Q

What is a conserved quantity?

A

Any quantity (measurable property) that remains constant through a process

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37
Q

What is a quantity?

A

A measurable property of matter.

Like mass, charge, etc.

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38
Q

True or False: A conserved quantity can exist even as the matter changes form

A

True

39
Q

What is the law of conservation of mass?

A

Mass can change form and be transferred from one object or place to another, but the total amount does not change.

40
Q

True or False: All physical properties will maintain the same mass from the beginning to the end of a process.

A

FALSE
There are a couple situations where mass changes.

41
Q

In what kind of science is conservation of mass especially important?

A

Chemistry. Chemical processes and the law of conservation go hand in hand.

42
Q

Conservation of fundamental particles

A

No matter how matter is changed, the number of fundamental elements of matter will always remain the same.

Elements of matter cannot be destroyed through processes of change. This is true for all of the 92 naturally occurring atoms.
(exceptions obviously, including atomic bombs)

43
Q

What is the cornerstone rule of chemistry?

A

There must always be the same number of atoms of each element at the beginning and end of a chemical reaction.

44
Q

How many types or classes of fundamental particles are there?

A

2

45
Q

What are the two types of fundamental particle classes?

A
  1. Leptons - includes electrons and electron-like particles, like muons, tauons, and neutrinos. 12 in total.
  2. Quarks - Makes up protons and neutrons
46
Q

What is a positron?

A

The anti-particle of each electron

47
Q

What is an anti-particle?

A

For each atomic particle, there is another kind of particle (the anti) that corresponds to it.

The anti-particle has charge and other features that are OPPOSITE from the particle.

48
Q

What is the mass of a photon?

A

Zero. How????

49
Q

True or False: Any lepton can be changed into a different lepton

A

True

50
Q

What is the law of the conservation of lepton number?

A

It says that in any reaction, leptons will change between different leptons, but the total number of leptons will always be the same.

51
Q

How many quarks are in a proton?

A

3

52
Q

How many quarks are in a neutron?

A

3

53
Q

True or False: A quark can change into another type of quark, thereby turning a neutron into a proton and vice versa

A

True

54
Q

What is the atomic mass number?

A

The total number of protons + neutrons in the nucleus of an atom.

55
Q

What is the law of conservation of atomic mass number?

A

Because quarks can turn into other quarks, protons and neutrons can turn into each other, but there will always be the same total number of protons and neutrons at the end.

56
Q

True or False: Rubbing a balloon on your head creates charge.

A

False
It redistributes existing charge.

57
Q

What is the law of conservation of charge?

A

The total amount of positive and negative charge will remain the same after any physical process.

58
Q

What is linear momentum?

A

An object’s mass times its velocity.

It measures the amount of motion in a straight line.

59
Q

True or False: Newton’s second law works at high speeds

A

False

60
Q

What is angular momentum?

A

The quantity that measures the amount of rotational motion an object has.

61
Q

What is the angular momentum equation?

A

Angular momentum = mass x speed x radius

62
Q

Why is a bike easier to keep upright at higher speeds?

A

Something that is spinning will keep spinning in the same direction (so they won’t wobble side to side).

63
Q

Why do objects that are spinning around in a circle (like a tetherball) speed up if they are brought closer to the center?

A

Because the law of conservation of angular momentum says mass x speed x radius must stay constant. So the speed increases when radius decreases to compensate.

64
Q

What is the law of conservation of energy?

A

Energy cannot be created or destroyed.

There are no exceptions to this law whatsoever.

65
Q

What is another name for the law of conservation of energy?

A

The First Law of Thermodynamics

66
Q

How fast does light travel?

A

300,000 km/s NO MATTER WHAT

67
Q

What happens to your length when you travel at extremely high speeds? (from an observer’s reference frame)

A

It gets shorter

68
Q

Do you travel slower or faster at high speeds? (from an observer’s reference frame)

A

Slower
Weird…

69
Q

What happens to your mass when you travel at extremely high speeds? (from an observer’s reference frame)

A

It increases

70
Q

What do Gedanken theories/examples rely on?

A

Reason and logic

71
Q

True or False: From different reference points, there can never be agreement on the simultaneity of events.

A

True

72
Q

True or False: Particles live for significantly longer when they are traveling close to the speed of light.

A

True
Time dilation

73
Q

True or False: Under the assumptions of time dilation, when you’re traveling at high speeds, it is only your clock that slows down, not you.

A

FALSE
Everything about your being is going slower at high speeds.

74
Q

How did Dr. Lawler use the bank/money system of America in an example?

A

She compared the federal reserve to the conservation laws. The amount of money in circulation will be constant, but the transactions that show how money changes hands and moves around the economy are what’s interesting.

75
Q

True or False: The conservation of angular momentum law will ALWAYS be true.

A

True

76
Q

When is the law of conservation of energy true?

A

True for all non-relativistic and non-nuclear situations

77
Q

True or False: The law of conservation of atomic mass number is ALWAYS true

A

True

78
Q

True or False: The law of conservation of charge is ALWAYS true.

A

True

79
Q

True or False: The law of conservation of leptons is ALWAYS true.

A

True

80
Q

True or False: The law of conservation of linear momentum is always true

A

True

81
Q

When is the law of conservation of mass true?

A

True for all non-relativistic and non-nuclear processes

82
Q

What are fundamental particles?

A

Basic particles that cannot be broken down into smaller pieces.

83
Q

What is linear momentum?

A

An object’s velocity x mass

84
Q

What is the mass number?

A

The sum of protons and neutrons in an atom.

85
Q

What are the six things that are conserved through transformation (that we’ll discuss in this class)?

A
  1. Mass
  2. Atomic mass number
  3. Charge
  4. Linear momentum
  5. Angular momentum
  6. Energy
86
Q

How would you describe the property of mass?

A

It is the property of an object that tells us how it resists being accelerated by a force.

87
Q

True or False: A plant that is growing will increase in mass equal to the sum mass of water and nutrients it is taking in to sustain growth.

A

True

88
Q

True or False: Mass can be negative

A

FALSE
It is either zero or positive

89
Q

What does it mean to be radioactive?

A

The nucleus is unstable

90
Q

What is the charge of a free neutron?

A

0

91
Q

What is an example of external forces and internal forces?

A

When a pool cue hits the white ball, it is an external force, but the balls all hitting each other are internal forces (not caused by an external force, all part of the same reaction)

92
Q

Which law cares most about external forces?

A

Conservation of linear momentum. Linear momentum is preserved UNLESS an external force acts upon it

93
Q
A

PHY S 100 (18 decks)

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