Which of the following situations violates the second law of
thermodynamics?
o
a. a heat pump absorbs 100 j of heat from a cool reservoir and
releases 80 j of heat to a hot reservoir.
o
b. a heat pump absorbs 100 j of heat from a cool reservoir and
releases 120 j of heat to a hot reservoir.
o
c. a heat engine absorbs 100 j of heat from a hot reservoir and
releases 70 j of heat to a cool reservoir.
o
d. a heat engine absorbs 100 j of heat from a hot reservoir and
releases 20 j of heat to a cool reservoir.

When you turn on a battery-operated device, an electrical circuit is

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Students in an introductory physics lab are performing an experiment with a parallel-plate capacitor made of two circular aluminum plates, each 11 cm in diameter, separated by 1.0 cm. how much charge can be added to each of the plates before a spark jumps between the two plates? for such flat electrodes, assume that value of 3×106n/c of the field causes a spark.