Is it a violation of the second law of thermodynamics to convert mechanical energy completely into heat? To convert heat completely into work? Explain your answers.
> At t = 0 a grinding wheel has an angular velocity of 24.0 rad/s. It has a constant angular acceleration of 30.0 rad/s2 until a circuit breaker trips at t = 2.00 s. From then on, it turns through 432 rad as it coasts to a stop at constant angular accelera
> A high-speed flywheel in a motor is spinning at 500 rpm when a power failure suddenly occurs. The flywheel has mass 40.0 kg and diameter 75.0 cm. The power is off for 30.0 s, and during this time the flywheel slows due to friction in its axle bearings. D
> A circular saw blade 0.200 m in diameter starts from rest. In 6.00 s it accelerates with constant angular acceleration to an angular velocity of 140 rad/s. Find the angular acceleration and the angle through which the blade has turned.
> A turntable rotates with a constant 2.25 rad/s2 angular acceleration. After 4.00 s it has rotated through an angle of 30.0 rad. What was the angular velocity of the wheel at the beginning of the 4.00-s interval?
> Tarzan, in one tree, sights Jane in another tree. He grabs the end of a vine with length 20 m that makes an angle of 45° with the vertical, steps off his tree limb, and swings down and then up to Jane’s open arms. When he arrives, his vine makes an angle
> A 90.0kg mail bag hangs by a vertical rope 3.5 m long. A postal worker then displaces the bag to a position 2.0 m sideways from its original position, always keeping the rope taut. (a) What horizontal force is necessary to hold the bag in the new positi
> When a gas expands adiabatically, it does work on its surroundings. But if there is no heat input to the gas, where does the energy come from to do the work?
> When a gas surrounded by air is compressed adiabatically, its temperature rises even though there is no heat input to the gas. Where does the energy come from to raise the temperature?
> In a constant-volume process, dU = nCV dT. But in a constant-pressure process, it is not true that dU = nCp dT. Why not?
> Applying the same considerations as in Question Q19.17, explain why the island of Niihau, a few kilometers to the southwest of Kauai, is almost a desert and farms there need to be irrigated. Question Q19.17: The prevailing winds on the Hawaiian island
> The prevailing winds on the Hawaiian island of Kauai blow from the northeast. The winds cool as they go up the slope of Mt. Waialeale (elevation 1523 m), causing water vapor to condense and rain to fall. There is much more precipitation at the summit tha
> What would be the efficiency of a Carnot engine operating with TH = TC ? What would be the efficiency if TC = 0 K and TH were any temperature above 0 K? Interpret your answers.
> In the carburetor of an aircraft or automobile engine, air flows through a relatively small aperture and then expands. In cool, foggy weather, ice sometimes forms in this aperture even though the outside air temperature is above freezing. Why?
> When you use a hand pump to inflate the tires of your bicycle, the pump gets warm after a while. Why? What happens to the temperature of the air in the pump as you compress it? Why does this happen? When you raise the pump handle to draw outside air into
> Real heat engines, like the gasoline engine in a car, always have some friction between their moving parts, although lubricants keep the friction to a minimum. Would a heat engine with completely frictionless parts be 100% efficient? Why or why not? Does
> An ideal gas expands while the pressure is kept constant. During this process, does heat flow into the gas or out of the gas? Justify your answer.
> Household refrigerators have arrays or coils of tubing on the outside, usually at the back or bottom. When the refrigerator is running, the tubing becomes quite hot. Where does the heat come from?
> The efficiency of heat engines is high when the temperature difference between the hot and cold reservoirs is large. Refrigerators, on the other hand, work better when the temperature difference is small. Thinking of the mechanical refrigeration cycle sh
> In an adiabatic process for an ideal gas, the pressure decreases. In this process does the internal energy of the gas increase or decrease? Explain.
> Imagine a gas made up entirely of negatively charged electrons. Like charges repel, so the electrons exert repulsive forces on each other. Would you expect that the temperature of such a gas would rise, fall, or stay the same in a free expansion? Why?
> An electric motor has its shaft coupled to that of an electric generator. The motor drives the generator, and some current from the generator is used to run the motor. The excess current is used to light a home. What is wrong with this scheme?
> Imagine a special air filter placed in a window of a house. The tiny holes in the filter allow only air molecules moving faster than a certain speed to exit the house, and allow only air molecules moving slower than that speed to enter the house from out
> When ice melts at 00C, its volume decreases. Is the internal energy change greater than, less than, or equal to the heat added? How can you tell?
> If you are told the initial and final states of a system and the associated change in internal energy, can you determine whether the internal energy change was due to work or to heat transfer? Explain.
> A pot is half-filled with water, and a lid is placed on it, forming a tight seal so that no water vapor can escape. The pot is heated on a stove, forming water vapor inside the pot. The heat is then turned off and the water vapor condenses back to liquid
> It is not correct to say that a body contains a certain amount of heat, yet a body can transfer heat to another body. How can a body give away something it does not have in the first place?
> For the following processes, is the work done by the system (defined as the expanding or contracting gas) on the environment positive or negative? (a). expansion of the burned gasoline–air mixture in the cylinder of an automobile engine; (b). opening a
> You bake chocolate chip cookies and put them, still warm, in a container with a loose (not airtight) lid. What kind of process does the air inside the container undergo as the cookies gradually cool to room temperature (isothermal, isochoric, adiabatic,
> The graph in Fig. P19.36 shows a pV-diagram for 3.25 mol of ideal helium (He) gas. Part ca of this process is isothermal. Fig. P19.36: (a). Find the pressure of the He at point a. (b). Find the temperature of the He at points a, b, and c. (c) How m
> Figure P19.35 shows the pV-diagram for a process in which the temperature of the ideal gas remains constant at 85°C. Figure P19.35: (a). How many moles of gas are involved? (b). What volume does this gas occupy at a? (c). How much work wa
> One-half mole of an ideal gas is taken from state a to state c as shown in Fig. P19.34. Fig. P19.34: (a). Calculate the final temperature of the gas. (b). Calculate the work done on (or by) the gas as it moves from state a to state c. (c). Does hea
> A quantity of air is taken from state a to state b along a path that is a straight line in the pV diagram (Fig. P19.33). Fig. P19.33: (a). In this process, does the temperature of the gas increase, decrease, or stay the same? Explain. (b). If Va = 0.
> A cylinder with a frictionless, movable piston like that shown in Fig. 19.5 contains a quantity of helium gas. Initially the gas is at 1.00 × 105 Pa and 300 K and occupies a volume of 1.50 L. The gas then undergoes two processes. In the firs
> Nitrogen gas in an expandable container is cooled from 50.0 0C to 10.0 0C with the pressure held constant at 3.00 × 105 Pa. The total heat liberated by the gas is 2.50 × 104 J. Assume that the gas may be treated as ideal. Find (a) the number of moles of
> Starting with 2.50 mol of N2 gas (assumed to be ideal) in a cylinder at 1.00 atm and 20.0 0C, a chemist first heats the gas at constant volume, adding 1.36 × 104 J of heat, then continues heating and allows the gas to expand at constant pressure to twice
> (a). One-third of a mole of He gas is taken along the path abc shown in Fig. P19.44. Assume that the gas may be treated as ideal. How much heat is transferred into or out of the gas? (b). If the gas instead went directly from state a to state c along th
> Figure P19.43 shows a pV-diagram for 0.0040 mol of ideal H2 gas. The temperature of the gas does not change during segment bc. Figure P19.43: (a). What volume does this gas occupy at point c? (b). Find the temperature of the gas at points a, b, and c
> Three moles of an ideal gas are taken around cycle acb shown in Fig. P19.42. For this gas, Cp = 29.1 J/mol ∙ K. Process ac is at constant pressure, process ba is at constant volume, and process cb is adiabatic. The temperatures of the g
> You hold an inflated balloon over a hot-air vent in your house and watch it slowly expand. You then remove it and let it cool back to room temperature. During the expansion, which was larger: the heat added to the balloon or the work done by the air insi
> Two moles of an ideal monatomic gas go through the cycle abc. For the complete cycle, 800 J of heat flows out of the gas. Process ab is at constant pressure, and process bc is at constant volume. States a and b have temperatures Ta = 200 K and Tb = 300 K
> Three moles of argon gas (assumed to be an ideal gas) originally at 1.50 × 104 Pa and a volume of 0.0280 m3 are first heated and expanded at constant pressure to a volume of 0.0435 m3, then heated at constant volume until the pressure reaches 3.50 × 104
> A volume of air (assumed to be an ideal gas) is first cooled without changing its volume and then expanded without changing its pressure, as shown by path abc in Fig. P19.39. Fig. P19.39: (a). How does the final temperature of the gas compare with it
> In a hospital, pure oxygen may be delivered at 50 psi (gauge pressure) and then mixed with N2O. What volume of oxygen at 20°C and 50 psi (gauge pressure) should be mixed with 1.7 kg of N2O to get a 50%/50% mixture by volume at 20°C? (a). 0.21 m3; (b). 0
> You have a cylinder that contains 500 L of the gas mixture pressurized to 2000 psi (gauge pressure). A regulator sets the gas flow to deliver 8.2 L/min at atmospheric pressure. Assume that this flow is slow enough that the expansion is isothermal and the
> In another test, the valve of a 500-L cylinder full of the gas mixture at 2000 psi (gauge pressure) is opened wide so that the gas rushes out of the cylinder very rapidly. Why might some N2O condense during this process? (a). This is an isochoric proces
> A thermodynamic system is taken from state a to state c in Fig. P19.38 along either path abc or path adc. Along path abc, the work W done by the system is 450 J. Along path adc, W is 120 J. The internal energies of each of the four states shown in the fi
> The power output of an automobile engine is directly proportional to the mass of air that can be forced into the volume of the engine’s cylinders to react chemically with gasoline. Many cars have a turbocharger, which compresses the air before it enters
> You place a quantity of gas into a metal cylinder that has a movable piston at one end. No gas leaks out of the cylinder as the piston moves. The external force applied to the piston can be varied to change the gas pressure as you move the piston to chan
> You compress a gas in an insulated cylinder— no heat flows into or out of the gas. The gas pressure is fairly low, so treating the gas as ideal is a good approximation. When you measure the pressure as a function of the volume of the ga
> You have recorded measurements of the heat flow Q into 0.300 mol of a gas that starts at T1 = 20.00C and ends at a temperature T2. You measured Q for three processes: one isobaric, one isochoric, and one adiabatic. In each case, T2 was the same. Figure P
> In a cylinder, 1.20 mol of an ideal monatomic gas, initially at 3.60 × 105 Pa and 300 K, expands until its volume triples. Compute the work done by the gas if the expansion is (a). isothermal; (b). adiabatic; (c). isobaric. (d). Show each process in
> Use the conditions and processes of Problem 19.56 to compute. Problem 19.56: A cylinder with a piston contains 0.150 mol of nitrogen at 1.80 × 105 Pa and 300 K. The nitrogen may be treated as an ideal gas. The gas is first compressed isobarically to ha
> A cylinder with a piston contains 0.150 mol of nitrogen at 1.80 × 105 Pa and 300 K. The nitrogen may be treated as an ideal gas. The gas is first compressed isobarically to half its original volume. It then expands adiabatically back to its original volu
> Use the conditions and processes of Problem 19.54 to compute. Problem 19.54: A cylinder with a piston contains 0.250 mol of oxygen at 2.40 × 105 Pa and 355 K. The oxygen may be treated as an ideal gas. The gas first expands isobarically to twice its or
> A cylinder with a piston contains 0.250 mol of oxygen at 2.40 × 105 Pa and 355 K. The oxygen may be treated as an ideal gas. The gas first expands isobarically to twice its original volume. It is then compressed isothermally back to its original volume,
> A monatomic ideal gas expands slowly to twice its original volume, doing 450 J of work in the process. Find the heat added to the gas and the change in internal energy of the gas if the process is (a). isothermal; (b). adiabatic; (c). isobaric.
> A certain ideal gas has molar heat capacity at constant volume CV. A sample of this gas initially occupies a volume V0 at pressure p0 and absolute temperature T0. The gas expands isobarically to a volume 2V0 and then expands further adiabatically to a fi
> An air pump has a cylinder 0.250 m long with a movable piston. The pump is used to compress air from the atmosphere (at absolute pressure 1.01 × 105 Pa) into a very large tank at 3.80 × 105 Pa gauge pressure. (For air, CV = 20.8 J/mol ∙ K.) (a). The pist
> When a system is taken from state a to state b in Fig. P19.37 along path acb, 90.0 J of heat flows into the system and 60.0 J of work is done by the system. Fig. P19.37: (a). How much heat flows into the system along path adb if the work done by the
> Discuss the application of the first law of thermodynamics to a mountaineer who eats food, gets warm and perspires a lot during a climb, and does a lot of mechanical work in raising herself to the summit. The mountaineer also gets warm during the descent
> During certain seasons strong winds called chinooks blow from the west across the eastern slopes of the Rockies and downhill into Denver and nearby areas. Although the mountains are cool, the wind in Denver is very hot; within a few minutes after the chi
> A cube of copper 2.00 cm on a side is suspended by a string. (The physical properties of copper are given in Tables 14.1, 17.2, and 17.3.) The cube is heated with a burner from 20.00C to 90.00C. The air surrounding the cube is at atmospheric pressure (1.
> The engine of a Ferrari F355 F1 sports car takes in air at 20.0°C and 1.00 atm and compresses it adiabatically to 0.0900 times the original volume. The air may be treated as an ideal gas with g = 1.40. (a) Draw a pV-diagram for this process. (b) Find t
> A cylinder contains 0.100 mol of an ideal monatomic gas. Initially the gas is at 1.00 × 105 Pa and occupies a volume of 2.50 × 10-3 m3. (a). Find the initial temperature of the gas in kelvins. (b). If the gas is allowed to expand to twice the initial vo
> During an adiabatic expansion the temperature of 0.450 mol of argon (Ar) drops from 66.0°C to 10.0°C. The argon may be treated as an ideal gas. (a). Draw a pV-diagram for this process. (b). How much work does the gas do? (c). What is the change in int
> A cylinder contains 0.0100 mol of helium at T = 27.0°C. (a). How much heat is needed to raise the temperature to 67.0°C while keeping the volume constant? Draw a pV-diagram for this process. (b). If instead the pressure of the helium is kept constant, h
> A cylinder contains 0.250 mol of carbon dioxide (CO2) gas at a temperature of 27.0°C. The cylinder is provided with a frictionless piston, which maintains a constant pressure of 1.00 atm on the gas. The gas is heated until its temperature increases to 12
> The temperature of 0.150 mol of an ideal gas is held constant at 77.0°C while its volume is reduced to 25.0% of its initial volume. The initial pressure of the gas is 1.25 atm. (a). Determine the work done by the gas. (b). What is the change in its inte
> Propane gas (C3H8) behaves like an ideal gas with γ = 1.127. Determine the molar heat capacity at constant volume and the molar heat capacity at constant pressure.
> An experimenter adds 970 J of heat to 1.75 mol of an ideal gas to heat it from 10.0°C to 25.0°C at constant pressure. The gas does +223 J of work during the expansion. (a). Calculate the change in internal energy of the gas. (b). Calculate g for the ga
> Suppose you try to cool the kitchen of your house by leaving the refrigerator door open. What happens? Why? Would the result be the same if you left open a picnic cooler full of ice? Explain the reason for any differences.
> Three moles of an ideal monatomic gas expands at a constant pressure of 2.50 atm; the volume of the gas changes from 3.20 × 10-2 m3 to 4.50 × 10-2 m3. Calculate (a). the initial and final temperatures of the gas; (b). the amount of work the gas does in
> In an experiment to simulate conditions inside an automobile engine, 0.185 mol of air at 780 K and 3.00 × 106 Pa is contained in a cylinder of volume 40.0 cm3. Then 645 J of heat is transferred to the cylinder. (a) If the volume of the cylin
> A gas in a cylinder expands from a volume of 0.110 m3 to 0.320 m3. Heat flows into the gas just rapidly enough to keep the pressure constant at 1.65 × 105 Pa during the expansion. The total heat added is 1.15 × 105 J. (a). Find the work done by the gas.
> Figure E19.8 shows a pV-diagram for an ideal gas in which its absolute temperature at b is one-fourth of its absolute temperature at a. Figure E19.8: (a). What volume does this gas occupy at point b? (b). How many joules of work was done by or on the
> An ideal gas is taken from a to b on the pV-diagram shown in Fig. E19.15. During this process, 700 J of heat is added and the pressure doubles. Fig. E19.15: (a). How much work is done by or on the gas? Explain. (b). How does the temperature of the g
> When water is boiled at a pressure of 2.00 atm, the heat of vaporization is 2.20 × 106 J/kg and the boiling point is 120°C. At this pressure, 1.00 kg of water has a volume of 1.00 × 10-3 m3, and 1.00 kg of steam has a volume of 0.824 m3. (a). Compute th
> The pV-diagram in Fig. E19.13 shows a process abc involving 0.450 mol of an ideal gas. Figure E19.13: (a). What was the temperature of this gas at points a, b, and c? (b). How much work was done by or on the gas in this process? (c) How much heat h
> A gas in a cylinder is held at a constant pressure of 1.80 × 105 Pa and is cooled and compressed from 1.70 m3 to 1.20 m3. The internal energy of the gas decreases by 1.40 × 105 J. (a). Find the work done by the gas. (b). Find the absolute value of the h
> The process abc shown in the pV-diagram in Fig. E19.11 involves 0.0175 mol of an ideal gas. Fig. E19.11: (a). What was the lowest temperature the gas reached in this process? Where did it occur? (b). How much work was done by or on the gas from a to
> Five moles of an ideal monatomic gas with an initial temperature of 127°C expand and, in the process, absorb 1500 J of heat and do 2100 J of work. What is the final temperature of the gas?
> In which situation must you do more work: inflating a balloon at sea level or inflating the same balloon to the same volume at the summit of Mt. McKinley? Explain in terms of pressure and volume change.
> Six moles of an ideal gas are in a cylinder fitted at one end with a movable piston. The initial temperature of the gas is 27.0°C and the pressure is constant. As part of a machine design project, calculate the final temperature of the gas after it has d
> (a). In Fig. 19.7a, consider the closed loop 1→ 3→ 2→ 4→ 1. This is a cyclic process in which the initial and final states are the same. Find the total work done by the system in thi
> A gas undergoes two processes. In the first, the volume remains constant at 0.200 m3 and the pressure increases from 2.00 × 105 Pa to 5.00 × 105 Pa. The second process is a compression to a volume of 0.120 m3 at a constant pressure of 5.00 × 105 Pa. (a)
> During the time 0.305 mol of an ideal gas undergoes an isothermal compression at 22.0 °C, 392 J of work is done on it by the surroundings. (a). If the final pressure is 1.76 atm, what was the initial pressure? (b). Sketch a pV-diagram for the process.
> The graph in Fig. E19.4 shows a pV-diagram of the air in a human lung when a person is inhaling and then exhaling a deep breath. Such graphs, obtained in clinical practice, are normally somewhat curved, but we have modeled one as a set of straight lines
> A thermodynamic system undergoes a cyclic process as shown in Fig. Q19.24. The cycle consists of two closed loops: I and II. (a). Over one complete cycle, does the system do positive or negative work? (b). In each loop, is the net work done by the syst
> A system is taken from state a to state b along the three paths shown in Fig. Q19.23. (a). Along which path is the work done by the system the greatest? The least? (b). If Ub > Ua, along which path is the absolute value of the heat transfer, |Q| , t
> The gas used in separating the two uranium isotopes 235U and 238U has the formula UF6. If you added heat at equal rates to a mole of UF6 gas and a mole of H2 gas, which one’s temperature would you expect to rise faster? Explain.
> If you run a movie film backward, it is as if the direction of time were reversed. In the time-reversed movie, would you see processes that violate conservation of energy? Conservation of linear momentum? Would you see processes that violate the second l
> Suppose that you put a hot object in thermal contact with a cold object and observe (much to your surprise) that heat flows from the cold object to the hot object, making the cold one colder and the hot one hotter. Does this process necessarily violate t
> Give two examples of reversible processes and two examples of irreversible processes in purely mechanical systems, such as blocks sliding on planes, springs, pulleys, and strings. Explain what makes each process reversible or irreversible.
> Are the earth and sun in thermal equilibrium? Are there entropy changes associated with the transmission of energy from the sun to the earth? Does radiation differ from other modes of heat transfer with respect to entropy changes? Explain your reasoning.
> The free expansion of an ideal gas is an adiabatic process and so no heat is transferred. No work is done, so the internal energy does not change. Thus, Q/T = 0, yet the randomness of the system and thus its entropy have increased after the expansion. Wh
> How can the thermal conduction of heat from a hot object to a cold object increase entropy when the same amount of heat that flows out of the hot object flows into the cold one?
> On a sunny day, large “bubbles” of air form on the sun warmed earth, gradually expand, and finally break free to rise through the atmosphere. Soaring birds and glider pilots are fond of using these “thermals” to gain altitude easily. This expansion is es
> In Example 20.4, a Carnot refrigerator requires a work input of only 230 J to extract 346 J of heat from the cold reservoir. Doesn’t this discrepancy imply a violation of the law of conservation of energy? Explain why or why not.
> Two moles of an ideal gas are compressed in a cylinder at a constant temperature of 65.0°C until the original pressure has tripled. (a). Sketch a pV-diagram for this process. (b). Calculate the amount of work done.
> A liquid is irregularly stirred in a well-insulated container and thereby undergoes a rise in temperature. Regard the liquid as the system. Has heat been transferred? How can you tell? Has work been done? How can you tell? Why is it important that the st
