## College Physics

Physics & Astronomy

## Quiz 11 :

Using Energy

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Q05 Q05 Q05

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a clockwise sense around the enclosed area, as shown on the figure, then the change of internal energy over the full cycle

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Q06 Q06 Q06

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a clockwise sense around the enclosed area, as shown on the figure, then the magnitude of the enclosed area represents

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Q07 Q07 Q07

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of a cycle, as shown in the pV diagram in the figure. If the process is carried out in a counter-clockwise sense around the enclosed area, as shown on the figure, then the magnitude of the enclosed area represents

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Q26 Q26 Q26

At room temperature, a typical person loses energy to the surroundings at the rate of 62 W. If this energy loss has to be made up by an equivalent food intake, how many kilocalories (food calories)does this person need to consume every day just to make up this heat loss? (1 cal = 4.186 J)

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Q27 Q27 Q27

A person running in place on an exercise machine for 10 min uses up 17 kcal (food calories). Another person exercises by repeatedly lifting two 2.5-kg weights a distance of 50 cm. How many repetitions of this exercise are equivalent to 10 minutes of running in place? Assume that the person uses negligible energy in letting down the weights after each lift. (1 cal = 4.186 J)

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Q30 Q30 Q30

The figure shows a pV diagram for a gas going through a cycle from A to B to C and back to A. From point A to point B, the gas absorbs 50 J of heat and finds its internal (thermal)energy has increased by 20 J. Going from B to C, the internal (thermal)energy decreases by 5.0 J.
(a)How much work was done by the gas from A to B?
(b)How much heat was absorbed by the gas from B to C?
(c)How much work was done by the gas going from B to C?

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Essay

Q42 Q42 Q42

The figure shows a pV diagram of a gas for a complete cycle. During part bc of the cycle, 1190 J of heat flows into a system, and at the same time the system expands against a constant external pressure of as its volume increases from to Calculate the change in internal (thermal)energy of the system during part bc of the cycle. If the change is nonzero, be sure to indicate whether the change is positive or negative.

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Q44 Q44 Q44

An ideal gas undergoes the process a→b→c→a shown in the pV diagram. The heat gained by the gas in process a→b is 546 J, while in process the gas loses 62.0 J of heat. In process a→b the gas performs of work, while in process c→a 223 J of work is done on the gas. How much heat is gained by the gas in process c→a?

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Q46 Q46 Q46

A 40.0-L container is divided into two equal parts by a rubber membrane. One half of the container has 1.50 moles of an ideal monatomic gas at 250 K, and the other half is a vacuum. The container is well insulated, so there is no exchange of heat with the surroundings. The membrane breaks, and eventually the gas reaches a new equilibrium condition occupying the entire volume. What is the final temperature of the gas?

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Q47 Q47 Q47

A cylinder contains 8.8 moles of ideal gas, initially at a temperature of 126°C. The cylinder is provided with a frictionless piston, which maintains a constant pressure of on the gas. The gas is cooled until its temperature has decreased to For the gas The ideal gas constant is R = 8.314 J/mol ∙ K. For this process, calculate:
(a)the work done by gas
(b)the net change in the internal (thermal)energy of the gas
(c)the heat transferred to the gas.

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Q48 Q48 Q48

An expandable container holds 2.30 mole of helium, He, gas with an initial pressure of 770 kPa and an initial volume of 2.10 L. The gas expands isothermally to a final pressure of 350 kPa. How much heat is gained by the gas during this process? (R = 8.31 J/mol ∙ K)

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Q49 Q49 Q49

A compression, at a constant pressure of 140 kPa, is performed on 4.0 moles of an ideal monatomic gas for which C

_{V}= 3/2 R. The compression reduces the volume of the gas from to What is the change in the internal (thermal)energy of the gas during this process? (R = 8.31 J/mol ∙ K)Free

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Q50 Q50 Q50

An expansion process on an ideal diatomic ideal gas for which C

_{V}= 5/2 R has a linear path between the initial and final coordinates on a pV diagram. The coordinates of the initial state are: the pressure is the volume is and the temperature is The final pressure is and the final temperature is What is the change in the internal (thermal)energy of the gas, during this process? (R = 8.31 J/mol ∙ K)Free

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Q52 Q52 Q52

A cylinder contains 10 moles of an ideal gas at a temperature of 300 K. The gas is compressed at constant pressure until the final volume equals 0.77 times the initial volume. The molar heat capacity at constant volume of the gas is 24.0 J/mol ∙ K and R = 8.31 J/mol ∙ K . How much heat is absorbed by the gas during this process? (R = 8.31 J/mol ∙ K)

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Q53 Q53 Q53

A cylinder contains 13 moles of an ideal gas at a temperature of 300 K. The gas is compressed at constant pressure until the final volume equal 0.70 times the initial volume. The molar heat capacity at constant volume of the gas is 24.0 J/mol ∙ K. What is the change in the internal (thermal)energy of the gas during this process? (R = 8.31 J/mol ∙ K)

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Q54 Q54 Q54

A sealed rigid tank contains 29 moles of an ideal gas, at an initial temperature of The pressure of the gas is increased until the final pressure equals 1.90 times the initial pressure. The heat capacity at constant pressure of the gas is How much heat is absorbed by the gas during this process? (R = 8.31 J/mol ∙ K)

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Q55 Q55 Q55

A sealed rigitd tank contains 30 moles of an ideal gas, at an initial temperature of The pressure of the gas is increased until the final pressure equals 1.40 times the initial pressure. The heat capacity at constant pressure of the gas is What is the change in the internal (thermal)energy of the gas during this process? (R = 8.31 J/mol ∙ K)

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Q75 Q75 Q75

The ocean thermal energy conversion project uses the surface water near tropical islands with a temperature of 20°C as the hot temperature reservoir, and the water at some depth, with a temperature of 5.0°C, as the cold temperature reservoir for a heat engine. What is the maximum possible efficiency of an engine running between those two temperatures?

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Q78 Q78 Q78

One of the most efficient engines built so far has the following characteristics: The combustion chamber temperature is 1900°C, the exhaust temperature = 430°C, 7.0 × 10

^{9}cal of fuel produces 1.4 × 10^{10}J of work in one hour. (1 cal = 4.186 J) (a)What is the actual efficiency of this engine? (b)What is the power output of this engine? (c)What would be the maximum possible efficiency for an engine using the same temperature extremes?Free

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Q79 Q79 Q79

A coal-fired plant generates 600 MW of electric power. The plant uses 4.8 × 10

^{6}kg of coal each day, and the heat of combustion of coal is 3.3 × 10^{7}J/kg. The steam that drives the turbines is at a temperature of 300°C, and the exhaust water is at 37°C. (a)What is the overall efficiency of the plant for generating electric power? (b)How much thermal energy is exhausted each day? (c)Using the same heat reservoirs, what is the maximum possible efficiency for a heat engine?Free

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Q82 Q82 Q82

A real (non-Carnot)heat engine, operating between heat reservoirs at temperatures of 450 K and 270 K, performs 3.3 kJ of net work, and rejects 8.2 kJ of heat in a single cycle.
(a)What is the thermal efficiency of this heat engine?
(b)What is the maximum efficiency it could possibly have?

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Q92 Q92 Q92

Suppose that the Department of Energy develops a new reversible engine that has a coefficient of performance (COP)of 4.0 when operated as a refrigerator and a COP of 5.0 when operated as a heat pump. What is its thermal efficiency when operated as a heat engine doing work?

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Q102 Q102 Q102

An ideal Carnot engine is operated as an air conditioner to cool a house in the summer. The air conditioner removes of heat per second from the house, and maintains the inside temperature at while the outside temperature is The power required to run the air conditioner under these operating conditions is closest to

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Q103 Q103 Q103

An ideal Carnot engine is operated as a heat pump to heat a room in the winter. The heat pump delivers heat to the room at the rate of 47 kJ per second and maintains the room at a temperature of 293 K when the outside temperature is 237 K. The power requirement to run the heat pump under these operating conditions is closest to

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