Which of the following correctly states the number of comets that scientists estimate to be located in the Oort cloud and the number that have actually been observed in the Oort cloud (with telescopes)?
A) estimated number in Oort cloud: 1 trillion
observed in Oort cloud: zero
B) estimated number in Oort cloud: 1 million
observed in Oort cloud: 1,000
C) estimated number in Oort cloud: 100,000
observed in Oort cloud: 50
D) estimated number in Oort cloud: 1 billion
observed in Oort cloud: 10,000
A) estimated number in Oort cloud: 1 trillion
observed in Oort cloud: zero
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a. Seyfert galaxies b. radio galaxies c. quasars
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A) -1/2 B) +1/2 C) -3/2 D) 0 E) +3/2
Suppose an equation relating position, x, to time, t, is given by x = bt3 + ct4, where b and c are constants. The dimensions of b and c are respectively:
a. T3, T4. c. L/T3, L/T4. b. 1/T3, 1/T4. d. L2×T3, L2×T4.
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A) 6.34 × 1018 photons/s B) 5.42 × 1018 photons/s C) 3.11 × 1018 photons/s D) 25.3 × 1018 photons/s E) 14.5 × 1018 photons/s