Question

A. A rigid tank contains a hot fluid that is cooled while being stirred by a paddle wheel. Initially, the internal energy of the fluid is 800 kJ. During the cooling process, the fluid loses 500 kJ of work on the fluid. Determine the final internal energy of the fluid. Neglect the energy stored in the paddle wheel.

B. Determine the power required for a 2000 kg car to climb a 100 m long uphill road with a slope of 30º (from horizontal) in 10 s (a) at a constant velocity, (b) from rest to a final velocity of of 30 m/s, and (c) from 35 m/s to a final velocity of 5 m/s. Disregard friction, air drag, and rolling resistance.

C. A university campus has 200 classrooms and 400 faculty offices. The classrooms are equipped with 12 fluorescent light bulbs each consuming 110 W, including the electricity used by the ballasts. The faculty offices, on average, have half as many light bulbs. The campus is open 240 days a year. The classrooms and faculty offices are not occupied an average of four hours a day, but the lights are kept on. If the unit cost of electricity is $0.075 kWh, determine how much the campus will save a year if (a) the lights in the classrooms and faculty offices are equipped with light sensors that turn off the lights during unoccupied periods. (b) the fluorescent lamps are replaced by LED lights each consuming an average of 10 W.

Answer 1

Cho nge in mternedl enevay Uf = 300 kJ 3 七 10,6 F = mg sine-2000 9800N mg sin θ Power 10