A refrigerator uses 40 J of work to extract heat from a heat reservoir at 
If the coefficient of performance of the refrigerator is 2.1, then how much heat is extracted from the heat reservoir at 
A. 48 J
B. 65 J
C. 84 J
D. 90 J
C. 84 J
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Suppose we launch a disk so it rolls without slipping up an incline. The disk of course slows down as it moves up the incline. But in what direction does the friction force acting on the disk point?
A. Up the incline B. Down the incline C. In some other direction (specify) D. The friction force is zero in this case.
A satellite of mass m has an orbital period T when it is in a circular orbit of radius R around the earth. If the satellite instead had mass 4m, its orbital period would be
A) 4T. B) 2T. C) T. D) T/2. E) T/4.
It is 6 km to Centerville, and you bicycle there in 20 minutes. Your speed is
A) 9 km/hr. B) 24 km/hr. C) 2 km/hr. D) 18 km/hr. E) 12 km/hr.
Which terrestrial world has the most atmosphere?
A) Venus B) Earth C) Mars D) Mercury.