Infrared radiation causes phosphors to give off visible light ?

Acommercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35°c by rejecting waste heat to cooling water that enters the condenser at 18°c at a rate of 0.25 kg/s and leaves at 26°c. the refrigerant enters the condenser at 1.2 mpa and 50°c. if the compressor consumes 3.3 kw of power, determine (a) the mass flow rate of the refrigerant, (b) the refrigeration load, (c) the cop, and (d) the minimum power input to the compressor for the same refrigeration load.

While carrying a heavy box up the stairs,you set the box on a step and rest. then you pick up the box and carry it to the top of the stairs. describe these actions in terms of balanced and unbalanced forces acting on the box.

There are multiple tuning forks present in the room, and annie strikes one with a natural frequency of 400 hz. which of these other tuning forks will begin to vibrate through resonance and make the sound louder? a 200 hz tuning fork a 400 hz tuning fork a 800 hz tuning fork a 1600 hz tuning fork