A refrigerator has a coefficient of performance equal to 4.2. How much work must be done on the operating gas in the refrigerator in order to remove 250 J of energy from the interior compartment?
A) 60 J
B) 120 J
C) 250 J
D) 480 J
E) 1050 J
A
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What temperature has the Big Bang has cooled to by now?
A) About 3,000 K B) 5,800 K C) About 300 K D) Just over 2.7K E) 1.4 K
A camera used for aerial mapping has a lens with a 30-cm diameter maximum aperture and a 42-cm focal length. Light of 550 nm wavelength is used to form the image
Assuming that the resolution of the camera is limited only by diffraction, what is the smallest angle (in milliradians) subtended by an object on the ground that can be resolved by this camera at maximum aperture? A) 1.6 mrad B) 2.2 mrad C) 3.2 mrad D) 4.5 mrad E) 6.3 mrad
A fire engine approaches a wall at 5 m/s while the siren emits a tone of 500 Hz frequency. At the time, the speed of sound in air is 340 m/s. How many beats per second do the people on the fire engine hear?
a. 0 b. 15 c. 29 d. 63 e. 250
The period of oscillation of a near-Earth satellite (neglecting atmospheric effects) is 84.3 min. What is the period of a near-Moon satellite? (RE = 6.37 × 10^6 m; RM = 1.74 × 10^6 m; ME = 5.98 × 10^24 kg; MM = 7.36 × 10^22 kg.)
a. 6.03 × 10^-3 min. b. 0.713 min. c. 84.3 min. d. 108 min. e. 140 min.