What conclusion can be drawn from the fact that some planets and satellites with solid surfaces have impact craters?
A. The Sun went through several explosions, ejecting material that scarred the planets and satellites.
B. The young planets had softer surfaces.
C. Collisions between Solar System bodies and planetesimals were common at one time.
D. Volcanoes were very active in the early stages of planet formation.
Answer: C
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Suppose you are observing a distant galaxy whose light has taken 12 billion years to reach us. What is the maximum age that this galaxy could have been when it emitted the light we are observing now? (Assume the age of the universe is about 14 billion years.)
A) about 2 billion years old B) about 10 billion years old C) about 4 billion years old D) about 12 billion years old
An object is moving with constant non-zero velocity in the +x-axis. The velocity versus time graph of this object is
A) a horizontal straight line. B) a vertical straight line. C) a straight line making an angle with the time axis. D) a parabolic curve. E) a hyperbolic curve.
When 10 kcal of heat is added to 2.0 kg of a substance, its temperature increases 20 C°. What is the specific heat of the substance?
In a hydrogen atom, a given electron has n = 7. How many possible values can ? have?
A) 6 B) 7 C) 15 D) 98