In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), we expect the term fciv to be small if
A) most civilizations destroy themselves within just a few hundred years of arising.
B) most of the civilizations that have ever existed are still out and about in the galaxy.
C) primitive life is common but intelligent life is rare.
D) most habitable planets never actually get life on them.
C
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The diagrams below show two uniformly charged spheres. The charge on the right sphere is 3 times as large as the charge on the left sphere. Which force diagram best represents the magnitudes and directions of the electric forces on the two spheres?
What factor caused different planets to form out of different types of material?
A) The angular momentum of the forming planet; faster rotating planets lost the lightest elements. B) The quantity of dust particles in the solar nebula; more dust caused some planets to contain heavier elements. C) The variation in temperature throughout the solar nebula; the higher the temperature, the lower the percentage of light elements in the forming planet. D) The angular momentum of the solar nebula pushed the heavy elements towards the outer regions of the nebula. E) The innate variation of chemical composition of the original nebula; the outer parts of the nebula contained a greater abundance of heavy elements.
Heat flow occurs between two bodies in thermal contact when they differ in what property?
a. mass b. specific heat c. density d. temperature
Assume that D and R have units of meters, T has units of seconds, m and M have units of kilograms, has units of meters per second, and has units of m/s2. Which of the following equations has self-consistent units?
A. D = mR2
B. m = M[1 + R2]
C. D = [1 – m/M]gT2
D. 
= mv2/R
E. D = 
2/RT
F. None of these can be correct.