Which are NOT fundamental particles?
A: Protons.
B: Quarks.
C: Leptons.
D: Bosons.
E: Electrons.
Ans: A: Protons.
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An engineer is designing a heating system that consists of multiple tubes placed in a duct carrying the air supply for a building. She decides to perform preliminary tests with a single copper tube, 2-cm-O.D., carrying condensing steam at 100°C. The air velocity in the duct is 5 m/s and its temperature is 20°C. The tube is placed normal to the flow, but it may be advantageous to place the tube at an angle to the air flow and thus increase the heat transfer surface area. It the duct width is 1 m, predict the outcome of the planned tests and estimate how the angle ? will affect the rate of heat transfer. Are there limits?
GIVEN
• A copper tube carrying condensed steam in an air duct
• Tube outside diameter (D) = 2 cm = 0.02 m
• Steam temperature (Ts) = 100°C
• Air velocity (U?) = 5 m/s
• Air temperature (T?) = 20°C
• Duct width (w) = 1 m
FIND
• Is it more advantageous to have the tubes normal to the air flow or at some angle to the air flow?
ASSUMPTIONS
• Steady state
• Air velocity in the duct is uniform
• Thermal resistance due to steam condensing is negligible
• Thermal resistance of the tube wall is negligible
SKETCH
PROPERTIES AND CONSTANTS
Thermal conductivity (k) = 0.0251 W/(m K) Kinematic viscosity
(?) = 15.7 × 10–6 m2/s Prandtl number (Pr) = 0.71
Astronaut Skip Parsec visits planet MSU8, which is composed of the same materials as Earth, but has twice the radius. If Skip weighs 800 N on Earth's surface, how much does he weigh on MSU8's surface?
A. 400 N B. 800 N C. 1600 N D. 3200 N
The mass enclosed in any orbit can be estimated from the equation M( A) The mass is spread out over large radius.
B) The mass is concentrated in the center.
C) The mass is distributed like a doughnut, with a hole in the center.
D) Cannot be determined from the information given.
Two point charges, separated by 1.5 cm, have charge values of +2.0 and -4.0 µC, respectively. Suppose we determine that 10 field lines radiate out from the +2.0-µC charge. If so, what might be inferred about the -4.0 mC charge with respect to field lines?
a. 40 radiate in c. 5 radiate out b. 20 radiate out d. 20 radiate in