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Principles of Physics: A Calculus-Based Text
- Show that the coefficients of performance of refrigerators and heat pumps are related by COPref=COPhp1. Start with the definitions of the COP s and the conservation of energy relationship between Qh, QC, and W.arrow_forwardWater falls over a dam of height h with a mass flow rate of R, in units of kilograms per second. (a) Show that the power available from the water is P=Rgh where g is the free-fall acceleration. (b) Each hydroelectric unit at the Grand Coulee Dam takes in water at a rate of 8.50 105 kg/s from a height of 87.0 m. The power developed by the falling water is converted to electric power with an efficiency of 85.0%. How much electric power does each hydroelectric unit produce?arrow_forwardConsider these scenarios and state whether work is done by the system on the environment (SE) or by the environment on the system (ES): (a) opening a carbonated beverage; (b) filling a flat tire; (c) a sealed empty gas can expands on a hot day, bowing out the walls.arrow_forward
- Which of the following is true for the entropy change of a system that undergoes a reversible, adiabatic process? (a) S 0 (b) S = 0 (c) S 0arrow_forwardFind the work done in the quasi-static processes shown below. The states are given as (p, V) values for the points in the PV plane: 1 (3 atm, 4 L), 2 (3 atm, 6 L), 3 (5 atm, 4 L), 4 (2 atm, 6 L), 5 (4 atm, 2 L), 6 (5 atm, 5 L) and 7 (2 atm, 5 L).arrow_forwardThe energy output of a heat pump is greater than the energy used to operate the pump. Why doesn't this statement violate the first law of thermodynamics?arrow_forward
- True or False: The entropy change in an adiabatic process must be zero because Q = 0.arrow_forwardConsider these scenarios and state whether work is done by the system on the environment (SE) or by the environment on the system (ES): (a) opening a carbonated beverage; (b) filling a flat tire; (c) a sealed empty gas can expands on a hot day, bowing out the walls.arrow_forwardIn a hydroelectric power plant, 65 m3/s of water flows from an elevation of 90 m to a turbine, where electric power is generated. The overall efficiency of the turbine–generator is 84 percent. Disregarding frictional losses in piping, estimate the electric power output of this plant.arrow_forward
- (a) If the internal energy of a systemincreases as the result of an adiabatic process, is work done on thesystem or by the system? (b) Calculate the work done on or by thesystem in part (a) if its internal energy increases by 670 Jarrow_forwardIn moving out of a dormitory at the end of the semester, a student does 1.82 x 104 J of work. In the process, his internal energy decreases by 4.07 x 104 J.Determine each of the following quantities (including the algebraic sign):(a)W,(b)U(c)Q.arrow_forwardWith 2.56×106J of heat transfer into this engine, a given cyclical heat engine can do only 1.50×105 J of work. (a) What is the engine's efficiency? (b) How much heat transfer to the environment takes place?arrow_forward
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