What happens to the core of a star after it ejects a planetary nebula?
A) It contracts from a protostar to a main-sequence star.
B) It becomes a neutron star.
C) It becomes a white dwarf.
D) It breaks apart in a violent explosion.
E) None of the above
C
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Because protostars are at a low temperature and surrounded by dust and gas, astronomers must observe them with ________.
A. ultraviolet telescopes B. gamma ray telescopes C. radar D. infrared and radio telescopes
A refrigerator has a coefficient of performance of 1.15, and it extracts 7.95 J of heat from the cold reservoir during each cycle
(a) How much work is done on the gas in each cycle? (b) How much heat is exhausted into the hot reservoir in each cycle?
A piston compresses a gas, while at the same time heat is lost to the surroundings. The temperature of the gas rises. This is governed by the __________ law of thermodynamics
Fill in the blank(s) with correct word
The ratio of the radius of a classical electron (re = kee2/mec2 = 2.8 × 10^?15 m) to the radius of a 4He nucleus (r = r0A1/3) is
a. 2.0 b. 0.68 c. 1.5 d. 0.92 e. 2.4