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Whether it is possible to transform mechanical energy into heat or internal energy completely and whether the reverse may happen or not.
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Answer to Problem 1Q
It is possible to transform mechanical energy into heat or internal energy completely, but the reverse may not happen.
Explanation of Solution
It is possible to convert all the mechanical energy into heat or internal energy. An example for such a case is that bringing an object moving on a surface to rest by means of friction. In such a case, the whole mechanical energy is dissipated as heat due to the friction force which oppose the motion of the object.
The complete transformation of heat into mechanical energy does not happen in the physical world. It can be assumed to happen in some ideal cases such as the adiabatic expansion of an ideal gas. According to second law of
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Chapter 20 Solutions
Physics for Scientists and Engineers with Modern Physics
- Consider 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_forwardGive an example of a spontaneous process in which a system becomes less ordered and energy becomes less available to do work. What happens to the system's entropy in this process?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
- 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_forwardIn a very mild winter climate, a heat pump has heat transfer from an environment at 5.00C to one at 35.0C. What is the best possible coefficient of performance for these temperatures? Explicitly show how you follow the steps in the Problem-Solving Strategies for Thermodynamics.arrow_forwardA car salesperson claims that a 300-hp engine is a necessary option in a compact car, in place of the conventional 130-hp engine. Suppose you intend to drive the car within speed limits ( 65 mi/h) on flat terrain. How would you counter this sales pitch?arrow_forward
- The insulated cylinder shown below is closed at both ends and contains an insulating piston that is flee to move on frictionless bearings. The piston divides the chamber into two compartments containing gases A and B. Originally, each compartment has a volume of 5.0102 m3 and contains a monatomic ideal gas at a temperature of and a pressure of 1.0 atm. (a) How many moles of gas are in each compartment? (b) Heat Q is slowly added to A so that it expands and B is compressed until the pressure of both gases is 3.0 atm. Use the fact that the compression of B is adiabatic to determine the final volume of both gases. (c) What are their final temperatures? (d) What is the value of Q?arrow_forwardA heat pump has a coefficient of performance of 3.80 and operates with a power consumption of 7.03 103 W. (a) How much energy does it deliver into a home during 8.00 h of continuous operation? (b) How much energy does it extract from the outside air?arrow_forwardOf the following, which is not a statement of the second law of thermodynamics? (a) No heat engine operating in a cycle can absorb energy from a reservoir and use it entirely to do work, (b) No real engine operating between two energy reservoirs can be more efficient than a Carnot engine operating between the same two reservoirs, (c) When a system undergoes a change in state, the change in the internal energy of the system is the sum of the energy transferred to the system by heat and the work done on the system, (d) The entropy of the Universe increases in all natural processes, (e) Energy will not spontaneously transfer by heat from a cold object to a hot object.arrow_forward
- (a) Ten grams of H2O stats as ice at 0 . The ice absorbs heat from the air (just above 0 ) until all of it melts. Calculate the entropy change of the H2O, of the air, and of the universe. (b) Suppose that the air in part (a) is at 20 rather than 0 and that the ice absorbs heat until it becomes water at 20 . Calculate the entropy change of the H2O, of the air, and of the universe. (c) Is either of these processes reversible?arrow_forwardThis problem compares the energy output and heat transfer to the environment by two different types of nuclear power stationsone with the normal efficiency of 34.0%, and another with an improved efficiency of 40.0%. Suppose both have the same heat transfer into the engine in one day. 2.501014J. (a) How much more electrical energy is produced by the more efficient power station? (b) How much less heat transfer occurs to the environment by the more efficient power station? (One type of more ef?cient nuclear power station, the gas—cooled reactor, has not been reliable enough to be economically feasible in spite of its greater eficiency.)arrow_forward(a) How much heat transfer occurs from 20.0 kg of 90.0C water placed in contact with 20.0 kg of 10.0C water, producing a final temperature of 50.0C ? (b) How much work could a Carnot engine do with this heat transfer, assuming it operates between two reservoirs at constant temperatures of 90.0C and 10.0C ? (c) What increase in entropy is produced by mixing 20.0 kg of 90.0C water with 20.0 kg of 10.0C water? (d) Calculate the amount of work made unavailable by this mixing using a low temperature of 10.0C, and compare it with the work done by the Garnet engine. Explicitly show how you follow the steps in the Problem-Solving Strategies for Entropy. (e) Discuss how everyday processes make increasingly more energy unavailable to do work, as implied by this problem.arrow_forward
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