You discover a binary star system in which one member is a15 solar mass main-sequence star and the other star is a 10 solar mass giant star. How do we believe that a star system such as this might have come to exist?
A) The two stars probably were once separate but became a binary when a close encounter allowed their mutual gravity to pull them together.
B) Other than the very low odds of finding a system with two such massive stars, there is nothing surprising about the fact that such systems exist.
C) The main-sequence star probably is a pulsating variable star and therefore appears to be less massive than it really is.
D) Although both stars probably formed from the same clump of gas, the more massive one must have had its birth slowed so that it became a main-sequence star millions of years later than its less massive companion.
E) The giant must once have been the more massive star but transferred some of its mass to its companion.
E
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A. 1100 m/s B. 980 m/s C. 910 m/s D. 840 m/s E. 770 m/s
Supermassive black holes are believed to be located at the center of many galaxies because
a. the rotation curve of the galaxy indicates that 90% of the galaxy is dark matter. b. the orbital motion of material near the center is very fast and indicates a very massive core. c. the shape of the bulge in all spiral galaxies can only be supported by a supermassive black hole. d. the spiral structure requires a black hole to maintain the spiral arms. e. the orbital speeds of a globular clusters in the galaxy are greater than the speed of light.
If you thrust a magnet into a closed loop of wire, the loop will
A) rotate. B) have a current in it. C) both of these D) neither of these
A reasonable estimate for the height of the walls in an ordinary American home is
A) 10 m. B) 8 m. C) 2.5 m. D) 1.5 m.