TEACHER'S TEACHERS'S TEACHER'S TEACHER'S
Ken Cheney
12/8/2005
4:21/C0
Physics 31A Test Seven
Title: SNOW POWER
1. You want to run an engine using the temperature difference between
your room, 24 C, and the snow outside, -24 C. What is the maximum
percent efficency?
a. 4.78
*b. 16.2
c. 23.6
d. 52.7
e. 70.8
Title: PANS AND HEAT TRANSFER
2. How thick (m) should the bottom of a pan be to transfer 650 watts
through an area of .23 square meters with a temperature difference of
17 K? Thermal conductivity is 4.5 watts m / (m m K)
a. .00859
*b. .0271
c. .0415
d. .0728
e. .0986
Type: P
Title: DEFINE
3. Define Isothrem, isobar, isometric, and adiabatic.
Title: TEMP AND SPEED
4. If the mass of a ZETA molecule is 33 kg and the mass of a UPAPA
molecule is 53 kg what is the ratio of the velocity of a ZETA molecule
to the velocity of a UPAPA molecule at the same temperature?
a. .609
b. .781
*c. 1.27
d. 2.53
e. 4.74
Title: BOILED MISSIONARY
5. A missionary is to be boiled in a large pot of water in the
morning. To conserve fuel the water is to be heated by 500 Kg of used
cannon balls heated to 400 degrees centigrade on a nearby volcano. He
expects to be put in 760 Kg of water at 24 degrees. How many Kg of ice
must he hide in the pot to keep the final temperature down to 50
degrees? Ignore the heat capacity of the pot and missionary. Heat of
fusion of ice = 79 cal/gm. Specific heat of iron = 0.1 cal/gm deg C
*a. -17.5
b. -16.1
c. -13.9
d. -10.6
e. -6.23
Type: P
Title: REVERSABLE
6. Show that no heat engine can be more efficent than a reversable
engine. Don't forget the Second Law.
Type: P
Title: DISCUSS THE SECOND LAW
7. Tell what you can about the Second Law of Thermodynamics, Entropy,
and the direction of time!