For a 10 mol mixture of air (8 mols nitrogen, N2, and 2 mols oxygen, O2) at 101 kPa, 20ºC, determine the mass concentration and the molar concentration of N2 and O2.
What will be an ideal response?
The mass concentrations are just the densities. The mixture volume is
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The average Reynolds number for air passing in turbulent flow over a 2-m-long flat plate is 2.4 x 106. Under these conditions, the average Nusselt number was found to be equal to 4150. Determine the average heat transfer coefficient for an oil having thermal properties similar to those in Appendix 2, Table 18 at 30°C at the same Reynolds number and flowing over the same plate.
GIVEN
Turbulent flow of air over a flat plate
Average Reynolds number (ReL) = 2.4 x 106
Plate length (L) = 2 m
Average Nusselt number (Nu) = 4150
FIND
Average heat transfer coefficient
ASSUMPTIONS
Steady state
Fully developed turbulent flow
Transition from laminar to turbulent flow occurs at Rex = 5 x 105
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 18, for oil at 30°C
Thermal Conductivity (k) = 0.11 W/(m K)
Kinematic Viscosity (v) = 15.4 ? 10–6 m2/s
Thermal Diffusivity (a) = 707 ? 10–10 m2/s
A thin 2.00-m string of mass 50.0 g is fixed at both ends and under a tension of 70.0 N. If it is set into small-amplitude oscillation, what is the frequency of the first harmonic mode?
A) 6.61 Hz B) 13.2 Hz C) 26.5 Hz D) 52.9 Hz
An alternative to the core-accretion theory that explains the formation of the jovian planets is the
A) differentiation theory. B) collision theory. C) gravitational instability theory. D) Big Bang theory. E) nebular contraction theory.
What evidence supports the existence of a black hole at the center of our galaxy?
A) The motions of the gas and stars at the center indicate that it contains 4 million solar masses within a region only 3 light-years across. B) We observe a large, dark object that absorbs all light at the center of our galaxy. C) We can see gas falling into an accretion disk and past the event horizon of a black hole. D) We observe an extremely bright X-ray source at the center of our galaxy. E) All of the above