A heat pump is capable of delivering more energy to the home than goes into the operation of the pump itself, when conditions are favorable. Which of the following statements is correct?
A. A heat pump violates the first law of thermodynamics
B. A heat pump, like the Carnot engine, is a theoretical device that is not useful in practice
C. A heat pump is more efficient when the outside temperature is colder
D. A heat pump violates the second law of thermodynamics
E. A heat pump transfers some energy from the outdoors
Answer: E
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A) emitted by Earth. B) emitted by the Sun. C) both of these D) neither of these
A uniform rod of mass M = 1.2 kg and length L = 0.80 m, lying on a frictionless horizontal plane, is free to pivot about a vertical axis through one end, as shown. The rotational inertia of the rod about this axis is given by (1/3)ML2. If a force (F = 5.0 N, ? = 40°) acts as shown, what is the resulting angular acceleration about the pivot point?
?
?
A. 16 rad/s2 B. 12 rad/s2 C. 14 rad/s2 D. 10 rad/s2 E. 33 rad/s2
A parachutist of mass 50.0 kg jumps out of an airplane at a height of 1 040 m. The parachute deploys, and she lands on the ground with a speed of 4.0 m /s. How much energy was lost to air friction during this jump?
a. 4.0E+2 J b. 8.2E+4 J c. 4.3E+5 J d. 5.1E+5 J e. 6.4E+5 J
Two small balls, A and B, attract each other gravitationally with a force of magnitude F. If we now double both masses and the separation of the balls, what will now be the magnitude of the attractive force on each one?
A) 16F B) 8F C) 4F D) F E) F/4