When the Moon passes directly between the Sun and the Earth, we see a lunar eclipse
Indicate whether the statement is true or false
FALSE
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Astronomers try to reconstruct our Galaxy's past from _____
A) its spherical component B) its disk component C) its spiral arms D) the stars of neighboring galaxies
A harmonic longitudinal wave propagating down a tube filled with a compressible gas has the form s(x, t) = smcos(kx??t). Its velocity can be obtained from
A. ?/k B. k/? C. k D. ? E. ?k
Calculate the overall heat transfer coefficient and the rate of heat flow from the hot gasses to the cold air in the cross flow tube-bank of heat exchanger shown in the accompanying illustration for the following operating conditions
Air flow rate = 0.4 kg/s.
Hot gas flow rate = 0.65 kg/s.
Temperature of hot gasses entering exchanger = 870°C.
Temperature of cold air entering exchanger = 40°C.
Both gases are approximately at atmospheric pressure.
GIVEN
? The crossflow tube bank heat exchanger shown above
? Air flow rate
( ma ) = 0.4 kg/s
? Gas flow rate
( mg) = 0.65 kg/s
? Entrance temperatures
? Air (Ta,in) = 40°C
? Gas (Tg,in) = 870°C
? Both gases are at 1 atm pressure
FIND
(a) The overall heat transfer coefficient
(b) The rate of heat transfer (q)
ASSUMPTIONS
? The hot gases have the same thermal properties as air
? No scaling
? Thermal resistance of the tube walls can be neglected
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at the entering temperatures
If an extrasolar planet suddenly became larger in radius, but kept the same mass and orbit, what would change in the observed Doppler shift of the star?
A) Nothing. The radius of a planet does not affect the Doppler shift. B) The time between peaks in the velocity of the star would decrease. C) The peak velocity of the star would be faster. D) The shape of the velocity curve would become less symmetric. E) The lowest velocity of the star would be slower.