A heat pump has a coefficient of performance of 4. If the heat pump absorbs 20 cal of heat from the cold outdoors in each cycle, the heat expelled (in cal) to the warm indoors is
A. 34
B. 25
C. 36
D. 40
E. 80
Answer: B
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The output voltage of an AC generator is of the form V = V0 sin(2?ft). A typical frequency in household circuits is 60 Hz. Using radians for angular measure in this equation, what is the factor 2?f in radians per second for this frequency?
a. 2? b. 120 c. 377 d. 60
A 3.0 cm tall statue is 24. cm in front of a concave mirror. The mirror radius of curvature is 20. cm
(a) Is the image real or virtual? (b) How far is the image from the mirror? (c) Is the image upright or inverted? (d) How high is the image?
Tripling the tension in a guitar string will change its natural frequency by what factor?
a. 3 c. 3–1/2 b. 31/2 d. 1.5
The distance to the sun is about 150 million km. Expressed in powers of ten, this is
A) 1.5 × 106 km. B) 1.5 × 108 km. C) 1.5 × 10-8 km. D) 1.5 × 10-6 km. E) None of the above.