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Condition |
free/or 0.5$ |
| 55743 | Give various examples of irreversible processes that occur in nature. Give an example of a process in nature that is nearly reversible. |
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| 55744 | A gasoline engine has a compression ratio of 6.00 and uses a gas for which y = 1.40. (a) What is the efficiency (b) What If? If the actual efficiency is 15.0%, what fraction of the fuel is wasted as a result of friction and energy losses by heat that could by avoided in a reversible engine? (Assume complete combustion of the air–fuel mixture.) |
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| 55745 | A gas is taken through the cyclic process described in Figure P20.30.
(a) Find the net energy transferred to the system by heat during one complete cycle.
(b) What If? If the cycle is reversed—that is, the process follows the path ACBA—what is the net energy input per cycle by heat? |
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| 55746 | Gas is contained in an 8.00-L vessel at a temperature of 20.0°C and a pressure of 9.00 atm. (a) Determine the number of moles of gas in the vessel. (b) How many molecules are there in the vessel? |
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| 55747 | A gas is compressed at a constant temperature. What happens to the mean free path of the molecules in this process? |
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| 55748 | A gas is compressed at a constant pressure of 0.800 atm from 9.00 L to 2.00 L. In the process, 400 J of energy leaves the gas by heat.
(a) What is the work done on the gas?
(b) What is the change in its internal energy? |
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| 55749 | A gas is at 0°C. If we wish to double the rms speed of its molecules, to what temperature must the gas be brought? |
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| 55750 | A gas consists of a mixture of He and N2 molecules. Do the lighter He molecules travel faster than the N2 molecules? Explain. |
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| 55751 | From the Maxwell–Boltzmann speed distribution, show that the most probable speed of a gas molecule is given by Equation 21.29. Note that the most probable speed corresponds to the point at which the slope of the speed distribution curve dNv / dv is zero. |
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| 55752 | A freely falling object requires 1.50 s to travel the last 30.0 m before it hits the ground. From what height above the ground did it fall? |
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| 55753 | For a Maxwellian gas, use a computer or programmable calculator to find the numerical value of the ratio Nv(v)/Nv(vmp) for the following values of v: v = (vmp/50), (vmp/10), (vmp/2), vmp, 2vmp, 10vmp, and 50vmp. Give your results to three significant figures. |
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| 55754 | For many years Colonel John P. Step, USAF, held the world’s land speed record. On March 19, 1954, he rode a rocket-propelled sled that moved down a track at a speed of 632 mi/h. He and the sled were safely brought to rest in 1.40 s (Fig. P2.31). Determine
(a) The negative acceleration he experienced and
(b) The distance he traveled during this negative acceleration. |
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| 55755 | Following a collision in outer space, a copper disk at 850°C is rotating about its axis with an angular speed of 25.0 rad/s. As the disk radiates infrared light, its temperature falls to 20.0°C. No external torque acts on the disk. (a) Does the angular speed change as the disk cools off? Explain why. (b) What is its angular speed at the lower temperature? |
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| 55756 | A flow calorimeter is an apparatus used to measure the specific heat of a liquid. The technique of flow calorimetry involves measuring the temperature difference between the input and output points of a flowing stream of the liquid while energy is added by heat at known rate. A liquid of density - flows through the calorimeter with volume flow rate R. At steady state, a temperature difference ΔT is established between the input and output points when energy is supplied at the rate μ. What is the specific heat of the liquid? |
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| 55757 | A firebox is at 750 K, and the ambient temperature is 300 K. The efficiency of a Carnot engine doing 150 J of work as it transports energy between these constant-temperature baths is 60.0%. The Carnot engine must take in energy 150 J/0.600 = 250 J from the hot reservoir and must put out 100 J of energy by heat into the environment. To follow Carnot’s reasoning, suppose that some other heat engine S could have efficiency 70.0%. (a) Find the energy input and wasted energy output of engine S as it does 150 J of work.
(b) Let engine S operate as in part (a) and run the Carnot engine in reverse. Find the total energy the firebox puts out as both engines operate together, and the total energy transferred to the environment. Show that the Clausius statement of the second law of thermodynamics is violated.
(c) Find the energy input and work output of engine S as it puts out exhaust energy of 100 J.
(d) Let engine S operate as in (c) and contribute 150 J of its work output to running the Carnot engine in reverse. Find the total energy the firebox puts out as both engines operate together, the total work output, and the total energy transferred to the environment. Show that the Kelvin–Planck statement of the second law is violated. Thus our assumption about the efficiency of engine S must be false.
(e) Let the engines operate together through one cycle as in part (d). Find the change in entropy of the Universe. Show that the entropy statement of the second law is violate |
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| 55758 | Find the instantaneous velocity of the particle described in Figure P2.3 at the following times:
(a) t = 1.0 s,
(b) t = 3.0 s
(c) t = 4.5 s, and
(d) t = 7.5 s |
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| 55759 | Figure Q20.14 shows a pattern formed by snow on the roof of a barn. What causes the alternating pattern of snow-covered and exposed roof? |
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| 55760 | Figure P2.24 represents part of the performance data of a car owned by a proud physics student.
(a) Calculate from the graph the total distance traveled.
(b) What distance does the car travel between the times t = 10 s and t = 40 s?
(c) Draw a graph of its acceleration versus time between t = 0 and t= 50 s.
(d) Write an equation for x as a function of time for each phase of the motion, represented by (i) 0a, (ii) ab, (iii) bc.
(e) What is the average velocity of the car between t = 0 and t = 50 s? |
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| 55761 | Figure P2.17 shows a graph of vx versus t for the motion of a motorcyclist as he starts from rest and moves along the road in a straight line.
(a) Find the average acceleration for the time interval t = 0 to t = 6.00 s.
(b) Estimate the time at which the acceleration has its greatest positive value and the value of the acceleration at that instant.
(c) When is the acceleration zero?
(d) Estimate the maximum negative value of the acceleration and the time at which it occurs. |
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| 55762 | Fifteen identical particles have various speeds: one has a speed of 2.00 m/s; two have speeds of 3.00 m/s; three have speeds of 5.00 m/s; four have speeds of 7.00 m/s; three have speeds of 9.00 m/s; and two have speeds of 12.0 m/s. Find
(a) The average speed,
(b) The rms speed, and
(c) The most probable speed of these particles. |
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