What is the main visual difference between the lunar highlands and the lunar maria? What are the implications of this observation?
What will be an ideal response?
The lunar highlands are very heavily cratered and the lunar maria are generally smooth. (More specifically, the maria contain only 3 percent as many craters per unit area as the highlands.) The difference in the amount of craters shows that the maria formed after the highlands, at the end of the heavy bombardment phase of the solar system. Radiometric dating of rocks from the highlands and maria shows that the heavy bombardment phase lasted no longer than a few hundred million years.
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Why are reflection nebulae blue in color?
What will be an ideal response?
The greenhouse effect keeps Venus hot because
a. the atmosphere contains free oxygen. b. the atmosphere is predominently carbon dioxide. c. the surface converts infrared into visible radiation. d. the surface is free of sulfur compounds. e. the magnetic field traps a large number of particles from the solar wind.
Of all the Galilean satellites, the surface of Europa is the youngest in age
Indicate whether the statement is true or false
A 2.54-cm-OD, 1.9-cm-ID steel pipe carries dry air at a velocity of 7.6 m/s and a temperature of –7°C. Ambient air is at 21°C and has a dew point of 10°C. How much insulation with a conductivity of 0.18 W/(m K) is needed to prevent condensation on the exterior of the insulation if h = 2.4 W/(m2 K) on the outside?
GIVEN
FIND
Thickness of insulation (t) required to prevent condensation
ASSUMPTIONS
Steady state
Flow is fully developed
Pipe surface temperature can be considered uniform and constant
Radiation heat transfer to the insulation is negligible or included in ch ? Pipe is 1% carbon steel
SKETCH
PROPERTIES AND CONSTANTS
for dry air at –7°C by extrapolation
the thermal conductivity of 1% carbon steel (ks) = 52 W/(m K)