You are studying a mystery companion to an evolved star, with mass transfer happening. Which of the following properties suggests that the companion is definitely a black hole?
A) The mystery companion has a mass of over 1.4 solar masses.
B) The mystery companion has a mass of over 3 solar masses.
C) The mystery companion has an X-ray emitting accretion disk.
D) The mystery companion gives off periodic X-ray bursts.
B
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Which of these hypothetical observations (none of them are real) would force us to reconsider our modern, Sun-centered view of the solar system?
a. We discover a small planet beyond Saturn that rises in the west and sets in the east each day. b. We find that we are unable to measure any parallax for a distant galaxy. c. We discover an Earth-sized planet orbiting the Sun beyond the orbit of Pluto. d. We discover that the universe is actually contracting, not expanding.
Structure 1 with member BC of length L/2 has force P1 applied at joint C. Structure 2 with member BC of length L has force P2 applied at C. Both structures have constant flexural rigidity EI. If the ratio of the applied forces P1/P2 5 5/2, the ratio of the joint B reactions RB1/RB2 is approximately:
(A) 1
(B) 5/4
(C) 3/2
(D) 2
If the Sun's rotation carries two sunspots around the side out of sight, you might see them again in about
A. two weeks. B. a month. C. six months. D. twelve hours.
Mass is a measure of
a. inertia. b. force. c. grams. d. weight. e. kilograms.