Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around supermassive black holes?
A) Observed radiation from the galactic center varies significantly in brightness in times as short as a few days.
B) Infrared observations show that many stars are forming near the centers of active galaxies.
C) Radio observations sometimes show long jets of material extending millions of light-years out from the galactic center.
D) The total amount of radiation coming from the galactic center is, in some cases, comparable to the amount of radiation put out by 10 billion or more ordinary stars.
E) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed.
B
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Power: The circuit power factor of an RC circuit is 0.620. The rms value of the ac voltage applied to this signal is 120 V and the impedance is 200 ?. What is the average power of this circuit?
A. 44.6 W B. 89.2 W C. 60.0 W D. 0.620 W E. 124 W
According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant?
A) hydrogen and helium gas; rock; metal; hydrogen compounds B) hydrogen and helium gas; hydrogen compounds; rock; metal C) hydrogen, water, methane, helium D) hydrogen compounds; hydrogen and helium gas; metal; rock
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 Kepler, the line from the Sun to any planet sweeps out equal areas of space
A) with each complete revolution. B) only when the paths are ellipses. C) in equal time intervals.