When a solid melts, energy is
A) absorbed by the solid.
B) released by the solid.
C) both of these
D) neither of these
Answer: A
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Venus may have started with an ocean's worth of water. Where is its water now?
A) The original water remains vaporized in the atmosphere due to Venus's intense heat. B) Most of the water is frozen beneath the surface. C) Most of the water combined with rocks in chemical reactions. D) The water was lost when ultraviolet light broke apart water molecules and the hydrogen escaped to space. E) The water changed to carbon dioxide through chemical reactions.
A block is supported on a compressed spring, which projects the block straight up in the air at velocity 
. The spring and ledge it sits on then retract. You can win a prize by hitting the block with a ball. When should you throw the ball and in what direction to be sure the ball hits the block? (Assume the ball can reach the block before the block reaches the ground and that the ball is thrown from a height equal to the release position of the block.)
A. At the instant when the block leaves the spring, directed at the block B. At the instant when the block leaves the spring, directed at the spring C. At the instant when the block is at the highest point, directed at the block D. At the instant when the block is at the highest point, directed at the spring E. When the block is back at the spring's original position, directed at that position
One of the "nails in the coffin" for the Earth-centered universe was
A) the retrograde motion of the planets. B) Galileo's observation of stars in the Milky Way. C) eclipses of the Sun. D) Galileo's observations of the moons of Jupiter. E) the phases of the Moon.
In a plot of probability of finding the electron in the hydrogen ground state versus the distance from the nucleus, the maximum occurs
a. at a0, the first Bohr radius. b. at slightly less than a0. c. at slightly more than a0. d. at 2 a0.