Q1 has 50 electric field lines radiating outward and Q2 has 250 field lines converging inward. What is the ratio Q1/Q2?
a. 5
b. ?5
c. 1/5
d. ?1/5
e. 0
d
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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
Observations indicate that it takes Saturn longer than Jupiter to complete one orbit about the Sun. This is in agreement with which of Kepler's laws?
A. First B. Second C. Third D. Fourth
Nanostructured materials can have unique properties. For materials with dimensions measured in nanometers the amount of surface energy is comparable to the bonding energy in the material.
(a) Compare the magnitude of the total surface energy to the total bond energy for a sphere of Ni atoms with one atom at the center surrounded by twelve nearest neighbors. The surface energy of Ni is 1.90 J/m2, the cohesive energy of Ni is –4.435 eV/atom, and the lattice parameter of FCC Ni is 0.352 nm. Assume that the total radius of this sphere is equal to 1 atomic diameter. (b) Is this 13-atom cluster of atoms stable?
When a rocket ship gaining speed in remote, gravity-free outer space runs out of fuel, it
A) gains speed for a short time, then slows down to a constant velocity. B) gains speed for a short time, slows down, and eventually stops. C) no longer gains speed. D) comes to a quick stop.