The lunar tides on Earth are making the Moon recede from Earth
a. True
b. False
Indicate whether the statement is true or false
True
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The density of interstellar dust is very low, yet it still blocks starlight because:
A) it is so cold it absorbs higher energy photons. B) there is 100 times more opaque gas than dust present in the ISM. C) the dust particles are about the same size as the light waves they absorb. D) the dust particles are irregular in shape. E) ice particles reflect all light back toward their stars, not toward us.
If a surface is illuminated by magenta light and the red is absorbed, then the color of the surface will appear as
A. green. B. yellow. C. blue. D. red.
A 3.2-L volume of neon gas (Ne) is at a pressure of 3.3 atm and a temperature of 330 K. The atomic mass of neon is 20.2 g/mol,
Avogadro's number is 6.022 × 1023 molecules/mol, and the ideal gas constant is R = 8.314 J/mol • K = 0.0821 L • atm/mol • K. The mass of the neon gas is closest to A) 7.9 × 10-3 kg. B) 4.6 × 10-3 kg. C) 3.8 kg. D) 7.8 kg. E) 7.8 × 102 kg.
A black sphere (2.5-cm in diameter) is placed in a large infrared heating oven whose walls are maintained at 370°C. The temperature of the air in the oven is 90°C and the heat-transfer coefficient for convection between the surface of the sphere and the air is 30 W/(m2 K). Estimate the net rate of heat flow to the sphere when its surface temperature is 35°C.
GIVEN
• A black sphere in a large infrared heating oven
• Sphere diameter (D) = 2.5 cm = 0.025 m
• Oven wall temperature (T2) = 370°C = 643 K
• Oven air temperature (T?) = 90°C = 363 K
• Convective heat transfer coefficient (hc) = 30 W/(m2 K)
• Sphere surface temperature (T1) = 35°C = 308 K
FIND
• The net rate of heat flow to the sphere (qtotal)
ASSUMPTIONS
• The oven walls are diffuse
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/m2K4