We say we are looking back in time when we are looking at the stars because
A) we see stars as they once were when their light reaches us.
B) space curves, we are actually looking at the past when we look in the night sky.
C) stars are emitting immense radiation, we are seeing processes that have already happened.
D) Earth's atmosphere bends and distorts their light.
Answer: A
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Suppose that the star Betelgeuse (the upper left shoulder of Orion) were to supernova tomorrow (as seen here on Earth). What would it look like to the naked eye?
A) Betelgeuse would remain a dot of light but would suddenly become so bright that for a few weeks we'd be able to see this dot in the daytime. B) We'd see a cloud of gas expanding away from the position where Betelgeuse used to be. Over a period of a few weeks, this cloud would fill our entire sky. C) Because the supernova destroys the star, Betelgeuse would suddenly disappear from view. D) Betelgeuse would suddenly appear to grow larger in size, soon reaching the size of the full Moon. It would also be about as bright as the full Moon.
Three equal charges of magnitude + 4.00 ?C are placed at the corners of an equilateral triangle of side 2.00 cm. What is the electric field potential energy of the system of these charges?
A) 90.0 J B) 900 mJ C) 0 J D) 216 mJ E) 21.6 J
The pressure drop in a tube carrying a viscous fluid is described by
A) Bernoulli's principle. B) Pascal's principle. C) Archimedes' principle. D) Poiseuille's equation. E) Newton's Second law.
At t = 0 the switch S is closed with the capacitor uncharged. If C = 30 ?F, ? = 30 V, and R = 5.0 k?, at what rate is energy being stored in the capacitor when I = 2.0 mA?
a.
32 mW
b.
40 mW
c.
44 mW
d.
36 mW
e.
80 mW