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PHY 126 Midterm Exam IIA
Chapters
15,16,17
Problem 1 ( 15+15 points)
A Styrofoam box used to keep drinks cold at a picnic has total wall area
(including the lid) of 0.80 m
2
and wall thickness 2.0 cm. Now it is filled with
ice at 0
o
C. If needed, use the thermal conductivity of Styrofoam is
0.010 W/(m K) and the heat of fusion of ice is 3.34 x 10
5
J/kg.
(a) What is the rate of heat flow into the box in J/s if the temperature of
the outside wall is 30
o
C? (15 points)
(b) How much ice in kg melts in one day? (15 points)
(Hint: We assume that the total heat flow is approximately the same as it
would be through a flat slab of area 0.80 m
2
and thickness 2.0 cm =
0.020 m.)
30
o
C
0
o
C
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View Full DocumentProblem 2 ( 7+7+8+8 points)
H
A jet of water is directed vertically
from a nozzle connected to a
reservoir through a pipe as shown
in Figure. The diameter of the nozzle
outlet is
and the jet operates H
under the surface of the water.
n
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 Summer '08
 Staff
 Physics

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