12/2/2010
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Quiz 1
Absolute zero is the temperature at which:
A. All motion ceases
B. Water freezes
C. Theoretically a gas has zero volume
D. All of the above
E. None of the above
Quiz 2
We vused which law to determine he
value of absolute zero:
A. Lambert’s Law
B. Boyle’s Law
C. Faraday’s Law
D. Charles Law
E. Kepler’s law
Jacques Alexandre César Charles
The gas increases by 1/273 of its
volume at 0°C for each °C rise of
temperature. This means that the
coefficient of expansion of all
gases is the same. The law is only
approximately true.
Quick Quiz
What is the most likely cause of error in the
determination of Absolute Zero done in lab?
• A. Human error
• B. Thermometer readings
• C. Syringe readings
• D. Some uncontrolled factor, like water vapor in
the air in syringe
• E. Gravity
Quiz 4: Who invented the artificial
machine?
Quiz 3: After who is he absolute temeprature scale named?
A. Celsius
B. Fahrenheit
C. Rankine
D. Kelvin
E. Charles
KELVIN, Lord (William Thomson)
(1824 - 1907)
• Proposed an absolute
scale of temperature in
1848.
Refrigeration
Apalachicola Museum
A. John Gorrie
First Ice Machine
Gorrie-1850
B. Lord Kelvin
C. John Carrier
D. Ferdinand Carre
E. Bernard Machen
Ferdinand Carre -developed successful Ice Business
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12/2/2010
Quiz 5: What is the name of the relativity you experience riding in a car
or an airplane?
A. Galilean relativity
B. Special relativity
C. General relativity
According to Galilean Relativity, the laws of mechanics are the same in
all inertial frames of reference
• An inertial frame of reference is one in which Newton’s Laws are
valid
• Objects subjected to no forces will move in straight lines
Galilean Relativity – Example
1852
There is a stationary
observer on the ground
Einstein’s Principle of Relativity
resolves problems without ether
• Postulates (1905)
– The Principle of Relativity: All the laws of physics are
the same in all inertial frames
– The constancy of the speed of light: the speed of light
in a vacuum has the same value in all inertial reference
frames, regardless of the velocity of the observer or the
velocity of the source emitting the light
 No preferred inertial reference frame exists
 It is impossible to detect absolute motion
 There is no such thing as absolute length
 There is no such thing as absolute time
 Events at different locations that are observed to occur simultaneously
in one frame are not observed to be simultaneous in another frame
moving uniformly past the first
Quick Quiz 7
The time interval Δt between two events measured by an observer
moving with respect to a clock is
A. longer than the time interval Δtp between the same two events
measured by an observer at rest with respect to the clock
B. shorter than the time interval Δtp between the same two events
measured by an observer at rest with respect to the clock
Quiz 8
A clock moving past an observer at speed v runs
A. more quickly than an identical clock at rest with respect to the
observer by a factor of -1
B. more slowly than an identical clock at rest with respect to the
observer by a factor of -1
Quick Quiz 6
An inertial reference frame is one which:
A. Is rotating
B. Is always stationary
C. Is at rest or moving at a constant velocity
D. Is accelerating
E. Is a fiction of the human mind
Identifying Proper Time
• The time interval Δtp is called the proper time
– The proper time is the time interval between events as measured by
an observer who sees the events occur at the same position
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The view of O’ that O is really the one moving with speed v to the left
and O’s clock is running more slowly is just as valid as O’s view that
O’ was moving
The principle of relativity requires that the views of the two observers
in uniform relative motion must be equally valid and capable of being
checked experimentally
All physical processes slow down relative to a clock when those
processes occur in a frame moving with respect to the clock-can be
chemical and biological as well as physical
Time dilation is a very real phenomena that has been verified by
various experiments
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12/2/2010
The Twin Paradox
• A thought experiment involving a set of twins, Speedo and Goslo
• Speedo travels to Planet X, 20 light years from earth-his ship travels at
0.95c
– After reaching planet X, he immediately returns to earth at the
same speed, keeping his eyes shut for the whole trip
• When Speedo returns, he has aged 13 years, but Goslo has aged 42
years
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Goslo’s perspective is that he was at rest while Speedo went on the
journey
Speedo thinks he was at rest and Goslo and the earth raced away
from him on a 6.5 year journey and then headed back toward him for
another 6.5 years
The paradox – which twin is the traveler and which is really older?
Quiz 10: In time dilation and length contraction the factor γ is
A. Less than 1
B. Greater than 1
C. Always equal to 1
L
LP

 LP 1 
v2
c2
The Twin Paradox – The Resolution
Quick Quiz 9
How can one twin or the other know detect a difference?
A. There is not—this is a flaw in the theory of relativity
B. One twin needs to have a pendulum
C. One twin needs psychological help after the trip
• Relativity applies to reference frames moving at uniform speeds
• The trip in this thought experiment is not symmetrical since
Speedo must experience a series of accelerations during the
journey
• Therefore, Goslo can apply the time dilation formula with a
proper time of 42 years
– This gives a time for Speedo of 13 years and this agrees with the earlier
result
• There is no true paradox since Speedo is not in an inertial frame
Pair Production
• An electron and a positron are produced
and the photon disappears
– A positron is the antiparticle of the
electron, same mass but opposite
charge
• Energy, momentum, and charge must be
conserved during the process
• The minimum photon energy required is
2me = 1.02 MeV
Quick Quiz 11
What is the frequency of the photon that produces a
pair with zero speed?
A. 1.02x1.6x10-19/6.2x10-34 = 2.6x1014 Hz
B. 1.02x106/6.2x10-34=1.6x1027 Hz
C. 1.02/6.2x10-34=2.6x1033 Hz
D. 1.02x106x1.6x10-19/6.2x10-34 = 2.6x1020 Hz
Pair Annihilation-Inverse of Pair Production
• In pair annihilation, an electronpositron pair produces two
photons
• It is impossible to create a single
photon
• Conserved
– Momentum
– Energy
– Charge
Quick Quiz: Which conservation law
dictates that 2 photons must be
produced?
A. Energy
B. Momentum
C. Charge
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