Which of the following does N* represent in the Drake equation, Nc = N* × fp × nHZ × fL × fI × fs?
A) The average number of planets in a solar system
B) The fraction of stars that have planets
C) The number of stars in our galaxy
D) The fraction of suitable planets on which life begins
C
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Young's Modulus: A 7.0-kg pipe is hung from a steel wire that is 2.5 m long and has a diameter of 0.75 mm. Young's modulus for steel is 2.0 × 1011 N/m2.(a) By what distance does the wire stretch?(b) If the wire diameter were doubled, what would be the stretch?
What will be an ideal response?
The slopes of Olympus Mons are relatively free of impact craters. What does this imply about its history?
A. Olympus Mons has erupted in the last 250 million years. B. Olympus Mons was once submerged in water. C. The mountain is tall enough to be eroded by planetary dust storms. D. It is one of the oldest features on Mars.
A square loop of wire has a current going around it. The magnetic field from the current on each side of the loop results in a magnetic force on the wire on the opposite side. Each resulting magnetic force on the opposite side wire
a. pushes inward on the loop. b. is actually zero since a current cannot push on itself. c. depends on whether the current is clockwise of counterclockwise. d. pushes outward on the loop.
Generally, the number of neutrons present in nuclei that are fission fragments is ________ the number of neutrons of corresponding nuclei of stable isotopes.
A. equal to B. greater than C. less than