The gas and dust in the disk of the Milky Way amount to approximately ________ of the mass of the stars.
A. 50%
B. 15%
C. 90%
D. 30%
Answer: B
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A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction. If the frequency of the siren is 500 Hz relative to the police car, what is the change in frequency (in Hz) heard by an observer in the truck as the two vehicles pass each other? (The speed of sound in air is 343 m/s.)
a. 242 b. 238 c. 240 d. 236 e. 234
Saturn's cloud layers are thicker than Jupiter's, due to Saturn's ________ gravity
Fill in the blank(s) with correct word
Stefan's Law says:
A) the hotter a star's surface, the bluer it looks to us. B) E = mc2. C) the energy radiated by a blackbody is proportional to T3. D) that if the Sun's temperature were doubled, it would give off 16X more energy. E) that doubling the star's temperature would also double its peak wavelength.
If the frequency of the AC voltage across an inductor is doubled, the inductive reactance of that inductor
A) decreases to one-half its original value. B) increases to twice its original value. C) decreases to one-fourth its original value. D) increases to 4 times its original value.