Given that the universe is about 14 billion years old, which of the following statements is logically valid?
A) All galaxies nearby us are about 14 billion years old.
B) All galaxies that we can see are about 14 billion years old.
C) All galaxies that we see have an age that is approximately equal to the age of the universe today, minus the lookback time (or light travel time) corresponding to the redshift of that galaxy.
D) The oldest galaxies we see at great distances are younger than the oldest galaxies we see nearby.
D
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Assume that the inner cylinder in Problem 7.40 is a heat source consisting of an aluminum-clad rod of uranium, 5-cm-OD and 2-m-long. Estimate the heat flux that raises the temperature of the bismuth 40°C and the maximum center and surface temperatures necessary to transfer heat at this rate.
GIVEN
Liquid bismuth flowing through an annulus
Annulus inside diameter (Di) = 5 cm = 0.05 m
Annulus outside diameter (Do) = 6.1 cm = 0.061 m
Bismuth velocity (V) = 4.5 m/s
Bismuth temperature (Tb) = 316°C
Inner cylinder is an aluminum clad uranium heat source
Cylinder length (L) = 2 m
From Problem 7.40: c h
26,800 W/(m2 K)
FIND
(a) The heat flux (QG/At) necessary to raise the bismuth temperature 40°C, and
(b) The maximum center (Tu,o) and surface (Tu,ro) temperatures of the uranium
ASSUMPTIONS
Steady state
The Bismuth temperature given is the bulk Bismuth temperature
Thermal resistance of the aluminum is negligible
Thickness of the aluminum is negligible
SKETCH
Uranus and Neptune both rotate ________ than the Earth does
Fill in the blank(s) with correct word
The diagram shows a circular wire loop of radius R carrying current I. What is the magnitude of the magnetic field, B, at the center of the loop?
If the wavelength of a light beam is doubled, what happens to the momentum of the photons in that light beam?
A) It is reduced by one-fourth of its original value. B) It is increased to four times its original value. C) It is doubled. D) It is halved. E) It stays the same.