The unified model describes active galactic nuclei using
a. a supermassive black hole at the center of a normal spiral galaxy.
b. a supermassive black hole surrounded by an accretion disk and dense disk of gas.
c. an accretion disk around a neutron star.
d. gravitational lenses to intensify the radiation coming from them.
e. different lines of sight toward and dwarf irregular galaxy.
b
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A bimetallic beam of aluminum (Ea 5 70 GPa) and copper (Ec 5 110 GPa) strips has a width of b 5 25 mm; each strip has a thickness of t 5 1.5 mm. A bending moment of 1.75 N?m is applied about the z axis. The ratio of the maximum stress in aluminum to that in copper is approximately:
(A) 0.6
(B) 0.8
(C) 1.0
(D) 1.5
A tropical year is the same as a sidereal year
Indicate whether the statement is true or false
A 1 300-kg automobile moving at 21 m/s has the brakes applied with a deceleration of 3.0 m/s2 . How far does the car travel before it stops?
a. 7.4E+1 m b. 1.5E+2 m c. 2.9E+5 m d. 2.3E+4 m e. 4.3E+2 m
Infrared waves are often called heat waves because they
40) A) emanate from relatively hot sources. B) consist of frequencies lower than those of visible light. C) induce resonance in molecules and increase internal energy in a substance. D) are the predominant waves emitted by the sun.