When a box rests on a round sheet of wood on the ground, it exerts an average pressure p on the wood. If the wood is replaced by a sheet that has four times the diameter of the original piece, what is the new average pressure

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

Explain why electric current cannot exist if a current doesn't have a voltage source.

What is the relationship between the direction of motion of the balloon and the wind currents