The fact that light travels only at 300,000 km/s in free space is a consequence of
A) electromagnetic wave propagation.
B) electromagnetic field induction.
C) Maxwell's laws.
D) energy conservation.
E) none of the above
Answer: D
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A 9.0-kg hanging weight is connected by a string over a pulley to a 5.0-kg block sliding on a flat table. If the coefficient of sliding friction is 0.19, find the tension in the string
?
?
a.
59.0 N
b.
67.5 N
c.
20.7 N
d.
37.5 N
A.A B.B C.C D.D E. Toward the viewer F. Away from the viewer T. The field is zero.
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by
A) the increase in forest fires during recent years. B) human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere. C) the human release of chemicals called CFCs into the stratosphere. D) the fact that our politicians spout a lot of hot air.
What evidence suggests that long gamma ray bursts originate from supernovae of stars massive enough to form black holes?
A) Some gamma ray bursts have been found to originate with galaxies that are actively forming stars, and would thus have a few very massive (but short lived) stars. B) Rapid observations in other wavelengths show that some gamma ray bursts coincide with points showing typical supernova light curves. C) The locations of gamma ray bursts suddenly begin blocking light from more distant stars. D) A and B E) B and C