A few decades ago, there was great controversy among astronomers over the question of quasar distances, with some arguing that quasars are much nearer than application of Hubble's law would seem to imply
Why do nearly all astronomers now agree that quasars really are quite far away? A) We now have images and spectra that show quasars to be embedded at the centers of distant galaxies and within distant galaxy clusters.
B) All quasars have large redshifts.
C) Now that we can explain bright quasar emission with power due to the presence of supermassive black holes, there is no reason to doubt that quasars are far away.
D) No one could think of a way to explain quasar speeds if they are nearby, so we concluded they must be far away.
A
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a. atoms b. isotopes c. elements d. cells e. nuclei
Ozone depletion in the upper atmosphere is likely to cause
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A toy rocket is launched vertically from ground level at time t = 0 s. The rocket engine provides constant upward acceleration during the burn phase
At the instant of engine burnout, the rocket has risen to 49.0 m and acquired an upward velocity of 60.0m/s The rocket continues to rise with insignificant air resistance in unpowered flight, reaches maximum height, and falls back to the ground. The maximum height reached by the rocket is closest to A) 221 m. B) 209 m. C) 244 m. D) 233 m. E) 256 m.
Two taut strings of identical mass per unit length are stretched with the same tension with their ends fixed, but one string is 0.330 cm longer than the other
Waves on these strings propagate at 34.0 m/s.The fundamental frequency of the shorter string is 258 Hz. What is the beat frequency when each string is vibrating at its fundamental frequency? A) 12.3 Hz B) 9.00 Hz C) 12.0 Hz D) 12.7 Hz E) 11.3 Hz