One of the most important features that must be explained by models during the formation of the galaxy is the ____
a. formation of spiral arms
b. differences in age and metallicity of stars, especially in the halo
c. formation of the central supermassive black hole
d. accumulation of dark matter in the corona
e. importance of spiral arms to star formation
b
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Two blocks of masses m1 and m2 are released from the top of two frictionless inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively
Which of the blocks is going faster when it reaches the bottom of its respective incline? A) We must know the actual masses of the blocks to answer. B) Both blocks have the same speed at the bottom. C) Block 1 is faster. D) Block 2 is faster. E) There is not enough information to answer the question.
How does Pluto's behavior at perihelion support its planetary status?
What will be an ideal response?
Within Earth's atmosphere the ozone layer is located:
A) in the troposphere. B) between the troposphere and the stratosphere. C) in the stratosphere. D) between the stratosphere and the mesosphere. E) in the mesosphere.
Evidence for a permafrost layer of ice just a few meters below the surface of Mars include:
A) outflow channels and ancient river deltas. B) "hydrated" chemical compounds found on surface rocks. C) carbonate rock layers that are in low abundance. D) "fluidized ejecta" craters. E) river channels and flood plains that look identical to such features on Earth.