In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), what do we mean by fnow?
A) the fraction of civilizations in the universe that currently are sending messages to us
B) the fraction of planets in the galaxy on which a civilization could theoretically develop right now
C) the fraction of all species ever to exist that we currently are aware of
D) the fraction of planets with civilizations at the present time (as opposed to only in the past or future)
D
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Earlier than a certain time, the laws of modern physics cannot describe the universe adequately. Roughly when is that time?
A: 10^43 seconds B: 10^33 seconds C: 1 minute D: 3 minutes E: 1 million years
Briefly describe the modern theory of how our Moon formed
What will be an ideal response?
A gas originally occupies a volume of 0.5 m3 at a pressure of 100 kPa. It is slowly allowed to expand until the volume is 2.5 m3. Assuming the temperature is kept constant, the final pressure will be
A. 10 kPa. B. 50 kPa. C. 500 kPa. D. 100 kPa. E. 20 kPa.
The motion of a piston in an auto engine is simple harmonic. If the piston travels back and forth over a distance of 10 cm, and the piston has a mass of 1.5 kg, what is the maximum speed of the piston and the maximum force acting on the piston when the engine is running at 4 200 rpm?