The best explanation for the activity at the center of the galaxy is a(n) ____
a. supercluster of O and B stars
b. black hole with a mass several thousand times the Sun's
c. giant atomic hydrogen cloud energized into a single, massive emission nebula
d. black hole with a mass several million times the Sun's
e. exotic object known as a "magnetar"
d
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An "onion skin" shell burning structure develops in:
A. a star much less massive than the Sun. B. a white dwarf. C. a star like the Sun. D. a neutron star. E. a star much more massive than the Sun.
When voltage is stepped up in a transformer, current is stepped down. But Ohm's law tells us that greater voltage means greater current, not less current. How then can current be lower when voltage is increased?
A) Current in the secondary is lower when compared to the greater current drawn by the primary. B) Ohm's law applies to the circuit connected to the secondary, not to the transformer. C) both of these D) neither of these
Compared to the critical density of matter, about how much matter and dark energy is there?
A) 1% matter, 99% dark energy B) 99% matter, 1% dark energy C) 100% matter, 0% dark energy D) 30% matter, 70% dark energy
A 60-kg skier pushes off the top of a frictionless hill with an initial speed of 4.0 m/s. How fast will she be moving after dropping 10 m in elevation? Air resistance is negligible
A) 10 m/s B) 15 m/s C) 0.15 km/s D) 0.20 km/s E) 49 m/s