If heat is flowing from a table to a block of ice moving across the table, which of the following must be true?
a. The table is rough and there is friction between the table and ice.
b. The ice is cooler than the table.
c. The ice is changing phase.
d. All three are possible, but none is absolutely necessary.
b
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In grinding a steel knife blade (specific heat = 0.11 cal/g-C°), the metal can get as hot as 400.°C. If the blade has a mass of 80
g, what is the minimum amount of water needed at 20°C if the water is not to rise above the boiling point when the hot blade is quenched in it?
Earth's rotation axis traces out a cone shape in the sky, precessing in the ___________________ direction
Fill in the blank(s) with correct word
Repeat Problem 9.23 for a tier of six horizontal 2.5-cm-OD tubes under similar thermal conditions.
GIVEN
? Saturated steam condensing on horizontal tubes
? Tube outside diameter (D) = 2.5 cm = 0.025 m
? Tube outer surface temperature (Ts) = 27°C
? Steam pressure (p) = 12 kPa
? Number of tubes (n) = 6
FIND
? The average heat transfer coefficient (hc)
ASSUMPTIONS
? Steady state
? Film condensation occurs
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 13, for saturated water at 12 kPa
Which of the following expresses the major idea of Hubble's Law?
A) There must have been a Big Bang. B) All galaxies are moving away from us equally fast. C) The more distant a galaxy is from us, the faster it moves away from us. D) The closer a galaxy is to us, the faster it moves away from us. E) More distant galaxies appear younger.