A refrigerator has a coefficient of performance of 4 . If the refrigerator absorbs 30 cal of heat from the cold reservoir in each cycle, the heat expelled (in cal) into the heat reservoir is
a. 40.5
b. 37.5
c. 36.5
d. 34.5
e. 22.5
b
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The electric field in the region defined by the y-z plane and the positive x axis is given by E = ax, where a is a constant. (There is no field for negative values of x.) As x increases in magnitude, relative to V = 0 at the origin, the electric potential in the region defined above is
A. a decreasing function proportional to ?|x2|. B. a decreasing function proportional to ?|x|. C. constant. D. an increasing function proportional to +|x|. E. an increasing function proportional to +|x2|.
What makes a reference system "inertial"?
a. Newton's first law applies in that system. b. Newton's second law applies in that system. c. Newton's third law applies in that system. d. Velocities add according to the rules of vector addition in that system. e. Newton's law of gravitation applies in that system.
What is the maximum number of eclipses that can occur in a year?
A. 7 (four solar and three lunar) B. 4 (two solar and two lunar) C. 2 (one solar and one lunar) D. 7 (five solar and two lunar) or 7 (four solar and three lunar) E. 7 (five solar and two lunar)
When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?
A) Copernicus used perfect circles for the orbits of the planets, though they are actually ellipses. B) Copernicus placed the planets in the wrong order going outward from the Sun. C) Copernicus misjudged the distances between the planets. D) Copernicus placed the Sun at the center, but did not realize that the Moon orbits Earth.