Exercises
and
Problems
275
For
Thought
and
Discussion
1.
If
system
A
is not in thennodynamic equilibrium with system
B,
and
B
is
not in equilibrium with C,
can
you draw any conclusions
about the temperatures
of
the three systems?
2.
Does a thennometer measure its own temperature
or
the tempera
ture
of
its surroundings? Explain.
3.
Compare
the relative sizes
of
the kelvin, the degree Celsius, the
degree Fahrenheit, and the degree Rankine.
4.
If
you
put
a
thennometer
in
direct sunlight, what do you measure:
the air temperature, the temperature
of
the Sun,
or
some
other
temperature?
5.
Why
does the temperature in a stone building usually vary less
than in a
wooden
building?
6.
Why
do
large bodies
of
water
exert a temperaturemoderating
effect
on
their surroundings?
Exercises
and
Problems
Exercises
Section 16.1 Heat, Temperature,
and
Thermodynamic
Equilibrium
14. A Canadian meteorologist predicts
an
overnight low
of
15°C.
How would a U.S. meteorologist express that
same
prediction?
15.
Nonnal
room
temperature
is
6S°F.
What
is this in Celsius?
16.
The
outdoor
temperature rises by 10°C.
What
is that rise
in
Fahrenheit?
17.
At
what temperature
do
the Fahrenheit and Celsius scales
coincide?
18. The
nonnal
boiling point
of
nitrogen is 77.3 K. Express this in
Celsius
and
Fahrenheit.
19. A sick child's temperature reads 39.1 on a Celsius thermometer.
What's
the
child's
temperature
on
the Fahrenheit scale?
Section 16.2
Heat
Capacity
and
Specific
Heat
20. Find the heat capacity
of
a
55tonne slab
of
concrete
(1 tonne
=
1000 kg).
21. Find the energy needed to raise a 2.0kg
chunk
of
aluminum by
lS°C,
22.
It
takes 7.5
kJ
to increase the temperature
of
a
Ikg
block
of
material
by
3.0°C.
What's
the material's specific heat?
23. The average
human
diet contains about
2000
kcal
per
day.
If
all
this food energy is released rather than stored as fat, what
is
the
approximate average power
output
of
the
human
body?
r;?
Walking
at
3
km/h
requires
an
energy expenditure rate
of
about
V
200
W~:How
far would you have to walk to "burn
off'
a 300kcal
hamburger?
25.
You
bring a 350g wrench into the house from your car.
The
house is 15°C
wanner
than the car,
and
it takes 2.52
kJ
of
energy
to
wann
the wrench by this amount. Find (a) the heat capacity
of
the wrench and (b) the specific
heat
of
the metal
it's
made from.
26. (a)
How
much heat does
it
take
to
bring a 3Akg iron skillet from
20°C to 130°C? (b)
If
the
heat
is supplied
by
a stove burner
at
the
rate
of
2.0 kW, how long will it take to
heat
the pan?
Section 16.3 Heat Transfer
27. Building
heat
loss in the United States is usually expressed in
Btulh.
What
is 1 Btulh in
SI
units?
28. Find the heatloss rate through a 1.0m2 slab
of
(a) wood and
(b) Styrofoam, each 2.0
cm
thick,
if
one
surface is
at
20°C and
the other at
O°C.
7. A
Thennos
bottle consists
of
an evacuated, doublewall glass
liner.
The
glass is coated with a thin
layer
of
aluminum. How
does a Thermos bottle work?
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 Winter '08
 Graham

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