Active galactic nuclei were first found through observations in the ____ wavelength band
a. visible
b. infrared
c. X-ray
d. radio
e. ultraviolet
d
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At t = 0, a wheel rotating about a fixed axis at a constant angular acceleration has an angular velocity of 2.0 rad/s. Two seconds later it has turned through 5.0 complete revolutions. What is the angular acceleration of this wheel?
a. 17 rad/s2 b. 14 rad/s2 c. 20 rad/s2 d. 23 rad/s2 e. 13 rad/s2
What is the name of the galaxy cluster to which the Milky Way belongs?
A. the Scorpius group B. the Sagittarius cloud C. M31 D. the local group E. the Virgo cluster
The quantum mechanical model of the hydrogen atom requires that if the orbital quantum number of the hydrogen atom is 7, there will be how many permitted orbital magnetic quantum numbers?
a. 6 b. 7 c. 14 d. 15 e. 49
A 2.5-cm-OD hot steam line at 100°C runs parallel to a 5.0-cm-OD cold water line at 15°C. The pipes are 5 cm center to center and deeply buried in concrete with a thermal conductivity of 0.87 W/(m K). What is the heat transfer per meter of pipe between the two pipes?
GIVEN
Hot pipe outside diameter (Dh) = 2.5 cm = 0.025 m
Hot pipe temperature (Th) = 100°C
Cold pipe outside diameter (Dc) = 5.0 cm = 0.05 m
Cold pipe temperature (Tc) = 15°C
Center to center distance between pipes (l) = 5 cm = 0.05 m
Thermal conductivity of concrete (k) = 0.87 W/(m K)
FIND
The heat transfer per meter of pipe (q/L)
ASSUMPTIONS
Two dimensional heat transfer between the pipes
Steady state conditions
Uniform thermal conductivity
SKETCH
