If gold were used as nuclear fuel, it would be best
A) fused.
B) fissioned.
C) either of these
Answer: B
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Two concentric spheres 0.2 m and 0.3-m in diameter, with the space between them evacuated, are to be used to store liquid air (133 K). If the surfaces of the spheres have been flashed with aluminum and the liquid air has a talent heat of vaporization of 209 kJ/kg, determine the number of kilograms of liquid air evaporated per hour.
GIVEN
• Two concentric spheres with the space between them evacuated and liquid air in the inner sphere
• Diameters ? D1 = 0.2 m ? D2 = 0.3 m
• Liquid air temperature (Ta) = 133 K
• Room temperature (T?) = 293 K
• Surfaces of the spheres have been flashed with aluminum
• Heat of vaporization of liquid air (hfg) = 209 kJ/kg = 209,000 J/kg
FIND
• The number of kilograms of liquid air evaporated per hour ( )m
ASSUMPTIONS
• Steady state
• Convective thermal resistance between the liquid air and interior sphere is negligible
• Thermal resistance of the sphere walls is negligible
• Natural convection on the exterior is negligible
• The room behaves as a blackbody enclosure
• The thickness of the sphere walls in negligible
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)
the hemispherical emissivity of the spheres will be approximated by that for oxidized aluminum at 310 K: ? = ?1 ? 2 = 0.11
Which of these gases is most responsible for the greenhouse effect on Earth?
a. oxygen (O2) b. nitrogen (N2) c. carbon dioxide (CO2) d. ozone (O3) e. ammonia (NH3)
Two harmonic waves are described by
What is the frequency (in Hz) of the resultant wave?
A. 300 B. 48 C. 8 D. 0.8 E. 150
A neutral atom has an electron configuration of 1s22s22p6. If a neutral atom holds one additional electron, what is the ground state configuration?
A) 1s22s22p63s1 B) 1s22s22p7 C) 1s22s32p6 D) 1s32s32p6 E) none of the given answers