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
b
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Which of these are good conductors?
A) feathers. B) wood. C) snow. D) all the above E) none of the above
An electron in the hydrogen atom has a wavelength of 2.67 nm. To what state of the hydrogen atom does this electron belong?
A) n = 2 B) n = 5 C) n = 8 D) n = 11 E) n = 14
A long-wavelength wave and a short-wavelength wave both move along the same rope. Which wave has the higher frequency, and which wave carries more energy, assuming their amplitudes are the same?
A) The short-wavelength wave has the higher frequency, but the two waves carry the same amounts of energy. B) The long-wavelength wave has the higher frequency and but the short-wavelength wave carries more energy. C) The long-wavelength wave has the higher frequency and carries more energy. D) The short-wavelength wave has the higher frequency and but the long-wavelength wave carries more energy. E) The short-wavelength wave has the higher frequency and carries more energy. E) no disturbance, because they cancel.
Tides are caused by
a. the gravitational pull of the Moon and the Sun. b. Earth's rotation. c. the Moon keeping the same face toward Earth. d. none of these.