What can cause a galactic fountain?
A) winds and jets from newly-formed protostars
B) a supernova occurring in the halo
C) multiple supernovae occurring together
D) the combined effect of spiral density waves
E) molecular clouds falling towards the galactic center
C
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Snell's Law: A beam of light, traveling in air, strikes a plate of transparent material at an angle of incidence of 56.0°. It is observed that the reflected and refracted beams form an angle of 90.0°. What is the index of refraction of this material?
A. 1.40 B. 1.43 C. 1.44 D. 1.48
How should the control volume method be implemented at an interface between two materials with different thermal conductivities? Illustrate with a steady, one-dimensional example. Neglect contact resistance.
GIVEN
Interface between two different materials with different thermal conductivities
FIND
(a) Difference equation at the interface
ASSUMPTIONS
No heat generation
SKETCH
According to the law of poles, like poles ______________
Fill in the blank(s) with correct word
Dr. X believes that the Hubble constant is H0 = 20 km/s/Mly while Dr. Y believes it is H0 = 24 km/s/Mly. Which statement below automatically follows?
A) Dr. X believes that the universe is expanding, but Dr. Y does not. B) Dr. X believes that the universe is older than Dr. Y believes. C) Dr. X believes that the universe has a much higher density than Dr. Y believes. D) Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever. E) Dr. X believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a slower speed than Dr. Y believes.