http://www.colorado.edu/physics/phys4230
Most all homework assignments will be due on Wednesdays
at 5:00 pm.
This first homework is due next Friday (January 23) since next
week is a short week.
Clicker Question
Clicker Question
What is the typical relaxation time for a oral medical thermometer?
A)
B)
C)
D)
E)
1 hour
3 minutes
30 seconds
1 microsecond
I thought this was a statistical mechanics class.
* Do not worry if you do not have your iClicker today.
When you are sitting on them, the wooden and metal toilet
seats have different?
A: Temperatures
B: Energy per particle
C: Heat
D: Relaxation times
E: Some intangible, metaphysical thing
Clicker Question
A gas at temperature T is mixture of hydrogen and
helium gas.
Which atoms have more
Kinetic Energy (on average)?
A: H
B: He
C: both have same KE
Reminders…
Reading for next week – Sections 1.6-1.7
Homework #1 due next Friday (January 23)
Make sure to start problems early
Additional office hours posted on web page
Answer: Both have the same average KE
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Clicker Question
Clicker Question
How many degrees of freedom in a 1D
simple harmonic oscillator?
Consider an ideal monatomic gas
confined to a plane, that is, 2 dimensions.
How many degrees of freedom are there?
A: 1
B: 2
C: 3
D: 4
E: Some other number
A: 1
B: 2
C: 3
D: 4
E: Some other number
Answer: There are 2 d.o.f, one for each of the
components of velocity squared in the KE
Answer: There are 2 d.o.f: 1 for the KE and one for the PE
Clicker Question
Clicker Question
Consider an ideal diatomic gas at high
temperature confined to a plane, that is,
2 dimensions.
How many degrees of freedom are there?
A gas expands at constant pressure.
P
P1
V
A: 2
B: 3
C: 4
D: 5
E: Some other number
V1
V2
Its internal energy U must…
A: increase
Answer: There are 5 d.o.f.: Two for translation, one for
rotation, and two for compression (one KE and one PE).
B: decrease
C: can’t tell
Answer: Since the temperature increases and U is
proportional to T, the internal energy must increase as well.
Clicker Question
A gas can be compressed from a given starting
pressure P and volume V by two methods
(isothermally or adiabatically).
Blue = isotherms
Reading for next week – Finish Chapter 1
Homework #1 due today (Friday Jan. 23) at 5 pm
Homework #2 due Wednesday, Jan. 28 at 5 pm
Pressure
Which of the two requires the smallest magnitude
of work?
A: Isothermal method
B: Adiabatic method
C: The same work.
Reminders…
Red = adiabatic
Starting Point
Answer: A – smallest integral
under the curve.
Vf
Vi
Volume
2
Clicker Question
For most materials, what is the sign of
∂V
∂T
P
A: Positive
B: Negative
C: Positive and Negative both occur frequently
Answer: Almost all materials expand when heated (but water
does NOT when it is between 0 and 4 deg C);
hence the sign mostly positive
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