Most of our knowledge of stellar evolution comes from studies of ________
Fill in the blank(s) with correct word
clusters
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Careful observations of the sky by ancient cultures served the practical purpose of
A) keeping track of time B) improving night vision C) religious worship D) keeping track of the changing position of the Earth around the Sun
A 10-meter-long spear is thrown at relativistic speeds through a 10-meter-long pipe. (Both these dimensions are measured when each is at rest.) When the spear passes through the pipe
A) the spear appears to shrink so the pipe completely covers it. B) the pipe appears to shrink so the spear extends from both ends. C) both appear to shrink equally so the pipe barely covers the spear. D) any of these, depending on the motion of the observer (moving with the spear, at rest with the pipe, and so on). E) none of the above
The horizontal surface on which the block slides is frictionless. If F = 20 N and M = 5.0 kg, what is the magnitude of the resulting acceleration of the block?
a.
5.3 m/s2
b.
6.2 m/s2
c.
7.5 m/s2
d.
4.7 m/s2
e.
3.2 m/s2
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
A) the high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle B) the smaller size of Venus, which has allowed it to lose much more internal heat than Earth C) the slow rotation of Venus D) the apparent lack of plate tectonics on Venus