A vessel containing 5.0 kg of water at 10°C is put into a refrigerator. The 1/7 HP motor (1 HP = 746 W) runs for 5.0 minutes to cool the liquid to the refrigerator's low temperature, 0°C. What is the COP of the refrigerator?
A. 5.7
B. 4.6
C. 6.5
D. 7.2
E. 3.6
Answer: C
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Imagine that, at a certain point in empty space, the curl of the magnetic field has a positive x component. What can we conclude from this information?
A. Ex must be positive at that point. B. Ex must be negative at that point. C. Ex must be zero at that point. D. Ex must be increasing with time at that point. E. Ex must be decreasing with time at that point. F. The magnetic field described is not physically possible. T. None of the above.
What use are 21 cm radio waves to Galactic astronomers?
A) They cut through the dusty cocoons to let us watch star birth. B) We can reflect them off the core of the Galaxy. C) Their Doppler shifts let us map the motions and locations of gas in the spiral arms. D) They bounce off stars like our Sun to let us precisely measure their distances. E) They pick up the cool, dark matter much better than can optical telescopes.
The Great ________ Spot of Neptune was striking in 1989, but gone by 1995
Fill in the blank(s) with correct word
Bree dips a pair of prongs onto a water surface and produces waves. When she dips more frequently the resulting waves
A) have shorter wavelengths. B) remain the same in wavelength. C) have longer wavelengths. D) move faster. E) none of the above