# • Exam information: Wednesday, in class. Covers Ch t 15 17 apters

```Notes
• Exam information: Wednesday, in class. Covers
Ch t 15-17.
Chapters
15 17
• Review Session: Tonight, 7:30-9:30pm, NSH 127
• Reminder: Problem Set due Friday before you leave
campus. Please put in box outside of my office.
• Colloquium Tomorrow: “Brian Greene: The State of
y , 4pm,
p , NSH 118
Stringg Theory”,
– Will have Office Hours from 5-6pm.
Temperature Scales, Temperature Measurement
A resistance thermometer is a device whose electrical
resistance (in Ohms, ) changes with temperature. A
certain resistance thermometer is found to have a
resistance of 90.35  when it is placed in water at the
triple-point temperature. What temperature is indicated
if it is placed in an environment where its resistance is
96.28 ? (Assume the resistance is absolutely linear
with temperature.) How would you calibrate the
Thermal Expansion
Thermal Expansion
Steel railroad tracks are laid when the temperature is
-5°C. A standard section of rail is 12.0 meters long.
What gap should be left between the rail sections so
that there is no compression when the temperature
gets as high as 42°C?
www.old-dalby.com/Research.htm
A physical pendulum, such as a clock, will expand or
contract given the ambient temperature.
a)Find
) d thee relative
e ve change
c ge in period
pe od P oof a pphysical
ys c
pendulum versus change in temperature, in terms of its
p
, .
linear coefficient of thermal expansion,
b)A clock pendulum made of invar ( = 0.7×10-6 per
°C)
C) has a period of 00.500
500 seconds and is accurate at
20°C. If the clock is used in an environment with an
average temperature of 30
30°C
C, what correction must be
made to the time after 30 days?
The Ideal Gas
A pipe closed at the top and open on the bottom contains air at
atmospheric pressure. The pipe is 25 m long. It is lowered
vertically into a freshwater lake until the water rises half-way up
the pipe,
pipe as shown in the figure.
figure What is the depth y of the waterwater
air interface below the surface? Assume the temperature is the
same everywhere
y
and is constant.
y
The best vacuum that can be attained in a laboratory is
about 10-18 atmospheres. How many molecules per
cubic centimeter are there in such a vacuum at 22°C?
A small hot air balloon has a volume of 15 m3. The air
inside is at an average temperature of 75°C, while the
air outside has a temperature of 24°C and an average
pressure of 1.0 atm. The balloon is tethered to prevent
it from floating away, and the tension in the rope is 10
Newtons. Assume the mass of air is 0.029 kg/mol, and
that the fabric of the balloon is massless. What is the
average pressure inside the balloon?
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