Elliot jumps up and down on a pogo stick. He has a mass of 60 kg, and his pogo stick has a spring with spring constant of 1100
N/m. What is his gravitational potential energy when he jumps
to a height of 0.25 m? Use 9.8 m/s/s for g.

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.