What happens to the internal energy of watere0d7 3;uosq+urdhrh . vapor in the air that condenses on the outside of a cold glass of water? Is work done or heat exchanged? Exph7ruro.d 0eduq hs3 ;+lain.

Use the conservation of energy to explain why the temperature uac5s cj2rf), of a gas increases when it is quickly compr2cs,5 c)ja furessed — say, by pushing down on a cylinder — whereas the temperature decreases when the gas expands.

In an isothermal process, 3700 J of work is donhjs1udox *00 guv+,q9 2eptbky sm*,v e by an ideal gas. Is this enough information to tell how much heat has been added to thsk,0g bo*v tu0qm2+, psde91y xvju *he system? If so, how much?

Is it possible for the temperature of a system to a14gu(xu9 tjc;:n, g9f8 6iwzf hot fbremain constant even though heat flo6: ,f9;a81gg9box( 4 ijh u wfftutnczws into or out of it? If so, give one or two examples.

Explain why the temperature of a gas increases when it is adiabatically coml. 67bius7z.rrtl.5 sapdo4w pressead.4b rt l.7ss6.pzir w5uol7d.

Can mechanical energy ever be transformed completely into he y6(0ca k+ 2ltxppvb:aat or internal energy? Can the reverse happen? In each case, if your answer is no, explain why no 2 tca k+xbvl0:pap6(yt; if yes, give one or two examples.

Can you warm a kitchen in winter by leaving the oven door open? Can you cosq81owsjh).zl m 66od bjz6g 0ol the kitchen on a hot summer day by leaving g 16 .s6mz j8ld)hzwbj0o oq6sthe refrigerator door open? Explain.

Would a definition of heat engine eff:a+yzjw1uep 5iciency as $e=W/Q_L$ be useful? Explain.

What plays the role of high-temperature and low-temperature areas in (a dhk9p wwx:6be3 c-7nwgs(hf.) an internal combustpxwngk97wes3 bw-fc:d ( h.6hion engine, and (b) a steam engine?

Which will give the greater improvement in the 6*1ls1cp5neky6z r au efficiency of a Carnot engine, a 6rl5u p 1a*1 nzkcyse610 $C^{\circ}\,$ increase in the high-temperature reservoir, or a 10 $C^{\circ}\,$ decrease in the low-temperature reservoir? Explain.

The oceans contain a tremendous amount of thermal (internal) energy. W30nm0;t2 pxwyv 6hbrtk+;c nmhy, in general, is it not possible to put this energy to usv2wc y t pr3;+06tnmx0hbkm;neful work?

A gas is allowed to expand (a) adiabatically and (b) isotheri8 w8uupv.3ac mally. In each process, does the entropy increase, decrease, or stay the same? E8a3.cp8u wuvixplain.

A gas can expand to twice its original voluy9e(jted;lc8 ehl 8 n:me either adiabatically or isothermally. Which process would result in a ge9 el;8c(td8lye jn:hreater change in entropy? Explain.

Give three examples, other than those mentioned in this Chapter, of cnp- 05y xd6 dw7bd/ hi**fo h4pv gdx)-ts9ewnaturally occurring processes in which order goes to disorder. Discuss the observability4x t/ydppbw)- o 7hh 9den6s*i*ddgf0wcx-v5 of the reverse process.

Which do you think has the greater entropy, 1 kg or43omhidnm.etk+e68 f solid iron or 1 kg of liquid t48rdm.6i nhemo 3+ekiron? Why?

(a) What happens if you remove the7f(n,l+ jl zyk lid of a bottle containing chlorine gas? (b) Does the reverse process ever happen? Why or why +(zyflj, 7nkl not? (c) Can you think of two other examples of irreversibility?

You are asked to test a machine that the inventor calls anue uyui t-:, 9 xr-p8mg/,oqbn “in-room air conditioner”: a big box, standing in the middle of the room, with a cable that plugs into a power outlet. When the machine is switched on, you feel a stream of cold air coming out of it. How do you know that this machine,o upbg-iu tyxr8e-n9 /,: mqu cannot cool the room?

Think up several processes (other than those a a(6ad fevq q/xk2w9+flready mentioned) that would obey the first law of thermodynamics, but, if they actually occurred, woul+fa6 v9ewak2x /q(fdqd violate the second law.

Suppose a lot of papers are strewn all over the floork)y4vef sd.eofs6 c- 64c j:bc; then you stack them neatly6cfs:d j 4sfvco6 by)e.4c-ek . Does this violate the second law of thermodynamics? Explain.

The first law of thermodynp saw9drtxnwpv480vpr 10tgw(87q)lamics is sometimes whimsically stated as, “You can’t get something for nothing,” and the second law as, “You can’t even break even.” Explain how these statements could be equivalent to the formal statent(7vl ps apg)v w0q9rxrp w01t4w88dments.

Entropy is often called “time’s arrow” beht/+z pq gpx0d y;r.1ycause it tells us in which direction natural processes occur. If a .y/0g;q+ 1xypdzth rpmovie were run backward, name some processes that you might see that would tell you that time was “running backward.”

Living organisms, as they grow, convert relatively simple food molecules bwgo/d4w( nrr/xi-4t 1k u7 clinto a complex structure. Is this a v4/xcbrrik-wdn t /1(gw l 7o4uiolation of the second law of thermodynamics?

  An ideal gas expands isothermally, performingozt+ a3ano45w;x xu3h slf+;c $ 3.40\times10^{ 3}J$ of work in the process. Calculate
(a) the change in internal energy of the gas,
(b) the heat absorbed during this expansion.    $J$

  A gas is enclosed in a cylinder fitted with a ligu*h (lf ,acxbfklz:3) rb0ls (ht frictionless piston and maintained at at(( ual30,:fchblx)*fz r s klbmospheric pressure. When 1400 kcal of heat is added to the gas, the volume is observed to increase slowly from $12m^3$ to $18.2m^3$ Calculate
(a) the work done by the gas .   $ \times10^{5 }$
(b) the change in internal energy of the gas.    $ \times10^{ 6}$

One liter of air is cooled at constant pressure until its volume is halved, ab-ci ;j f s8;;.+cckv)8uagit8wwap ond then it is allowed to expand isothermally bacuk;)cct f8p+i aa;gcbv8 -.8 swowji;k to its original volume. Draw the process on a PV diagram.

Sketch a PV diagram of the following process: 2.0 L of ideal gas at atmosphll2bf/88k1ksi 5 vqf zeric pressure are cooled at constant pressure to a volume of 1.0 L, and then expanded isothermally back to 2.0 L, whereupon the zsl/v8k81q 2kfilb5fpressure is increased at constant volume until the original pressure is reached.

A 1.0-L volume of air initiad c lda.;x(su p;-pw8tlly at 4.5 atm of (absolute) pressure is allowed to expand isothermally until th;dl;t.xwsp (dup a 8-ce pressure is 1.0 atm. It is then compressed at constant pressure to its initial volume, and lastly is brought back to its original pressure by heating at constant volume. Draw the process on a PV diagram, including numbers and labels for the axes.

  The pressure in an idej 86n9s kagi3nal gas is cut in half slowly, while being kept in a container with ri6j nn sk3agi89gid walls. In the process, 265 kJ of heat left the gas.
(a) How much work was done during this process?    $J$
(b) What was the change in internal energy of the gas during this process?    $kJ$

  In an engine, an almost ideal gas is compressed adiabatically to half v 8/wq4chw g hi-xz 1vufsav;9 62.jtvits volume. In doing j;-h4ift v1 wvx28s96wcug.z/hvavqso, 1850 J of work is done on the gas.
(a) How much heat flows into or out of the gas?    $J$
(b) What is the change in internal energy of the gas?    $J$
(c) Does its temperature rise or fall? ----待选择----fallrise 

  An ideal gas expands at a constant total pressure of 3u uuf+n1 syofclwwg1-60- k1pjt+f8 a.0 atm from 400 mL to 660 mL. Heat then flows out of the gas at constant volume, and the pressure and temperature are allowed to drop until the1 f uu+ugw+11 folk0nys af68tj -c-pw temperature reaches its original value. Calculate
(a) the total work done by the gas in the process,   $J$
(b) the total heat flow into the gas.    $J$

  One and one-half moles of a o s*x 50i 0aiwwl.;5 7-uhbiptaqr7jyn ideal monatomic gas expand adiabatically, performing 7500 J of work ia7iy*pu; 75.woqi b-sxwtj5rl h0i0 an the process. What is the change in temperature of the gas during this expansion?   $ K$

  Consider the following twojsf .bvoj7 )p s2n,5;; olx: rjbce6qbly e:-x-step process. Heat is allowed to flow out of an ideal gas at constant volume so that its pressure drops from 2.2 atm to 1.4 atm. Then the gas expands at constant pressure, from a volume of 6.8 L to 9.3 L, where the temperature reaches its original value. See Fig. 15–2;;b.n-xj )e:xj c5 sfl7boojpb: vsl,q6eyr22. Calculate
(a) the total work done by the gas in the process,    $J$
(b) the change in internal energy of the gas in the process,    $J$
(c) the total heat flow into or out of the gas.    $J$  ----待选择----intoout  the gas

  The PV diagram in Fig. 15–23 shows two possible states of a systok2j :+p lh4d mszk,8 )qtofo.em containing 1.35 moles of a mo2+zpqo , tlm4sk.k oj:f)o 8hdnatomic ideal gas.$(P_1\,=\,P_2\,=\,455N/m^2,V_1\,=\,2.00m^3,V_2\,=\,8.00m^3)$
(a) Draw the process which depicts an isobaric expansion from state 1 to state 2, and label this process A.
(b) Find the work done by the gas and the change in internal energy of the gas in process A. W =    $J$ $\Delta\,U$ =    $J$
(c) Draw the two-step process which depicts an isothermal expansion from state 1 to the volume $V_2$ followed by an isovolumetric increase in temperature to state 2, and label this process B.
(d) Find the change in internal energy of the gas for the two-step process B.    $J$

  When a gas is taken from a to c along the curved path in Fig. 15–24, the wo3gje9i:noe.dw6 dy7 kmhv ) d;rk done9 7.)noj :hwy gkd;6vided 3me by the gas is $W\,=\,-35\,J$ and the heat added to the gas is $Q\,=\,-63\,J$ Along path abc, the work done is $W\,=\,-48\,J$
(a) What is Q for path abc?    $J$
(b) If $P_c\,=\,\frac{1}{2}P_b$ what is W for path cda?    $J$
(c) What is Q for path cda?    $J$
(d) What is $U_a-U_c$?    $J$
(e) If $U_d-U_c\,=\,5J$ what is Q for path da?    $J$

  In the process of taking a gas from state a to state c along the curvem q(ao,5tgnh )g6i;ci du t.k/d path shown in Fig. 15–24, hid.(6n/m 5oa,iq) tk c;ggut80 J of heat leaves the system and 55 J of work is done on the system.
(a) Determine the change in internal energy, $U_a-U_c$.    $J$
(b) When the gas is taken along the path cda, the work done by the gas is How much heat Q is added to the gas in the process cda?    $J$
(c) If $ P_a\,=\,2.5P_d$ how much work is done by the gas in the process abc?    $J$
(d) What is Q for path abc?    $J$
(e) If $U_a-U_b\,=\,10\,J$ what is Q for the process bc?    $J$
Here is a summary of what is given:
$\begin{aligned}
Q_{\mathrm{a} \rightarrow \mathrm{c}} & =-80 \mathrm{~J} \\
W_{\mathrm{a} \rightarrow \mathrm{c}} & =-55 \mathrm{~J} \\
W_{\mathrm{cda}} & =38 \mathrm{~J} \\
U_{\mathrm{a}}-U_{\mathrm{b}} & =10 \mathrm{~J} \\
P_{\mathrm{d}} & =2.5 P_{\mathrm{d}} .
\end{aligned}$

  How much energy would the person of Example 15–8 trl 2* jg-fpwna 9*h2ivtansform if instead of working 11.0 h she took a noog-itf22havl wp*9* n jntime break and ran for 1.0 h?    $ \times10^{ 7}J$

  Calculate the average metabolic rate of a person who sleeps 8.0 h, sitst;;pn ,gx x9ootr5*tj at a desk 8.0 h, engages in light activity 4.0 h, watches television 2.0 h, plays tennis 1.5 hn5o t p,o* jrtxx;tg9;, and runs 0.5 h daily.    $W$

  A person decides to lose weight by sleeping one hour less per day, using the ti(/k9c4o),(m f ec z suovteeu)me for light activity. How much weight (or mass) can this person expect to lose in 1 year, assuming no change in food intake? Assume that 1 kg of fat stores about 40,000 kJ of oeee(cu(c/ ozf,ts))4u mkv9energy.   kg(retain one decimal places)    $lbs$

  A heat engine exhausts 8200 J of heat while performis d8dmx;or u*1ng 3200 J of useful work. What is the efficiency of this engine?ou8sdd x1r*m;    %

  A heat engine does 9200 J of stef6w( p8u0abfgsr, g v j)2/work per cycle while absorbing 22.0 kcal of heat from a high-temperature fa)g6,f2e8 0 sbg/( prjwsvtu reservoir. What is the efficiency of this engine?    %

  What is the maximum efficiency of a heat engine whose o 9,5rszpeaqyhf/4an .perating temperatures are9, a/eaz.f5nhy4 rps q 580$^{\circ}\,C$ and 380$^{\circ}\,C$?   %

  The exhaust temperature of a heat engine is 2r1l-b+ m j-zo2ecerbb* )(xn him.hd330$^{\circ}\,C$. What must be the high temperature if the Carnot efficiency is to be 28%?    $^{\circ}\,C$

  A nuclear power plant operates at qm.ah pp *zm (hz5(ro+75% of its maximum theoretical (Carnot) efficiency between temperatures of 625ha.( hqrp(zmpzom5* +$^{\circ}\,C$ and 350$^{\circ}\,C$. If the plant produces electric energy at the rate of 1.3 GW, how much exhaust heat is discharged per hour?    $ \times10^{13 }J/h$

  It is not necessary that a heat engine’s hot environment be hotttttxix72te: 8 g d:lvv.plc8/er than ambient temperature. Liquid nitrogen (77 K) is about as cheap as bottled water. What would be the efficiency of an engine that .7i8c:p vl ttte8lxdgv :2tx/ made use of heat transferred from air at room temperature (293 K) to the liquid nitrogen “fuel” (Fig. 15–25)?    %(Round to the nearest integer)

  A Carnot engine performs work at the rate of 440 kW wv14o( qs9yvjav; mqxbume+1mk 3g7 o-hile using 680 kcal of heat per second. If the temperature of the heat source is bmv(+ q34axe1 9mvg1;k uj7o-yovsmq570$^{\circ}\,C$, at what temperature is the waste heat exhausted?    $^{\circ}\,C$

  A Carnot engine’s operating temed rys691t0ov)b a+q0.ulne r peratures are 210$^{\circ}\,C$ and 45$^{\circ}\,C$. The engine’s power output is 950 W. Calculate the rate of heat output.    $W$

  A certain power plant puts we8 5opd-rd h(re+oa/:yrqpzt)5x2eout 550 MW of electric power. Estimate the heat discharged per second, assuming that ta5 2qrow) /:eh8ot(5 r rdz+edp-yepxhe plant has an efficiency of 38%.    $MW$

  A heat engine utilizes a heat sours9yt2;inp 89ifn)whoce at 550$^{\circ}\,C$ and has an ideal (Carnot) efficiency of 28%. To increase the ideal efficiency to 35%, what must be the temperature of the heat source?    $^{\circ}\,C$

  A heat engine exhausts its heat at uwx yd ( yg**dfoj)u):uns+0h 350$^{\circ}\,C$ and has a Carnot efficiency of 39%. What exhaust temperature would enable it to achieve a Carnot efficiency of 49%?    $^{\circ}\,C$

  At a steam power plant, steam engines3xg3fqm , o 69 :pzoxkthn38qb work in pairs, the output of heat from one being the approximate heat input of the secondhqf3gnxx 6o8:,qb t3o9p 3zmk . The operating temperatures of the first are 670$^{\circ}\,C$ and 440$^{\circ}\,C$, and of the second 430$^{\circ}\,C$ and 290$^{\circ}\,C$. If the heat of combustion of coal is $ 2.8\times10^{7 }\,J/kg$ at what rate must coal be burned if the plant is to put out 1100 MW of power? Assume the efficiency of the engines is 60% of the ideal (Carnot) efficiency.    $kg/s$

  The low temperature of a freezer c)t:j r;jhrc 4uqufb,-ooling coil is -15$^{\circ}\,C$ and the discharge temperature is 30$^{\circ}\,C$. What is the maximum theoretical coefficient of performance?   

  An ideal refrigerator-freezer operates wittwa mp;n+ xjcs8v318xh a in a 24$^{\circ}\,C$ room. What is the temperature inside the freezer?    $K$

  A restaurant refrigerator has a coefficient of performance of 5.0. If thm5 3j1*a:lf cvwr) nqxe temperature in the kitchen outside the refrige:n *f3x5m1r vw)lqjacrator is 29$^{\circ}\,C$, what is the lowest temperature that could be obtained inside the refrigerator if it were ideal?    $^{\circ}\,C$

  A heat pump is used to keep )2lfapcyz-c k, 5siqk)bd-v2 a house warm at 22$^{\circ}\,C$. How much work is required of the pump to deliver 2800 J of heat into the house if the outdoor temperature is
(a) 0$^{\circ}\,C$,    $J$
(b) -15$^{\circ}\,C$ Assume ideal (Carnot) behavior.    $J$

  What volume of water atry-rf +-5npl6zl( ses 0$^{\circ}\,C$ can a freezer make into ice cubes in 1.0 hour, if the coefficient of performance of the cooling unit is 7.0 and the power input is 1.0 kilowatt?    $L$

  An ideal (Carnot) enginw/+ 74d w3wuu r hy2utk;-tkagkj24npe has an efficiency of 35%. If it were possible to run it backward as a heat pump, what would be its coeph ;u 7+ 42/t-tkku32 yuganjwdw r4kwfficient of performance?   

  What is the change in entri u1iskcgfsh7+d* 8 z rlva/)1opy of 250 g of steam at 100$^{\circ}\,C$ when it is condensed to water at 100$^{\circ}\,C$?    $J/K$

  One kilogram of water is hrkws(cdg)j +( eated from 0$^{\circ}\,C$ to 100°C. Estimate the change in entropy of the water.    $J/K$

  What is the change in entropy oh1 fxm(rp - tyl3t76bif $1\,m^3$ of water at 0$^{\circ}\,C$ when it is frozen to ice at 0$^{\circ}\,C$?   $ \times10^{6 }\, J/K $

  If $1.00\,m^3$ of water at 0$^{\circ}\,C$ is frozen and cooled to -10$^{\circ}\,C$ by being in contact with a great deal of ice at -10$^{\circ}\,C$ what would be the total change in entropy of the process?   $J/K$

  A 10.0-kg box having an initial speed (a; rs+tmn e ia:1 e 2+cmuvlg:)xobf6of $3.0m/s$ slides along a rough table and comes to rest. Estimate the total change in entropy of the universe. Assume all objects are at room temperature (293 K).   $J/K$

A falling rock has kineticcsijlc +:zv l:(x/yoen4h:e6;j i(u z energy KE just before striking the ground and coming to rest. zx::uceyo;(sz l lje 6n:v /4jchii(+ What is the total change in entropy of the rock plus environment as a result of this collision?

  An aluminum rod conduc 01wp29vlpv9rh3 nsig dd0sh 8ts $7.50\,cal/s$ from a heat source maintained at 240$^{\circ}\,C$ to a large body of water at 27$^{\circ}\,C$. Calculate the rate entropy increases per unit time in this process.   $\frac{J/K}{s}$

  1.0 kg of water at 3s. lvi t0eu8x/0$^{\circ}\,C$ is mixed with 1.0 kg of water at 60$^{\circ}\,C$ in a well-insulated container. Estimate the net change in entropy of the system.    $J/K$

  A 3.8-kg piece of aluminum at9+d 9 lvwi,hi.qkt1 nk 30$^{\circ}\,C$ is placed in 1.0 kg of water in a Styrofoam container at room temperature (20$^{\circ}\,C$). Calculate the approximate net change in entropy of the system.    $J/K$

  A real heat engine working between heat reservoirs at 970 K j tufd0pl):*w7t1 0 zu oeizp7and 650 K produces 550 J of wp 01l u*uedztztoi7j70wf: p) ork per cycle for a heat input of 2200 J.
(a) Compare the efficiency of this real engine to that of an ideal (Carnot) engine.    % of ideal(Round to the nearest integer)
(b) Calculate the total entropy change of the universe per cycle of the real engine.    $J/K$
(c) Calculate the total entropy change of the universe per cycle of a Carnot engine operating between the same two temperatures.   

  Calculate the probabilities, when you throw twojd79 b -wz)-,qtai eur7zy;wa dice, of obtaining
(a) two numbers totaling 5. The probability is 1/  
(b) two numbers totaling 11. The probability is 1/  

Rank the following five-card hands in order of increasing probabilitye9--y:w jwytvg o z(;v: (a) four aces and a king; (b) six of hearts, eight of diamonds, queen of clubs, three of hearts, jack ozy-yt v:9v- gww;je( of spades; (c) two jacks, two queens, and an ace; and (d) any hand having no two equal-value cards. Discuss your ranking in terms of microstates and macrostates.

  Suppose that you repeatedly shake six coins in your hand and drop them ydn0.6hzr*ar on the floor. Codyz.r0a *h6 rnnstruct a table showing the number of microstates that correspond to each macrostate. What is the probability of obtaining
(a) three heads and three tails,   /64
(b) six heads?   /64

  Solar cells (Fig. 15–26) can produce about 40 W of electricity peuf6fml s;l2 qo1k87izr square meter of surface area if directly faci;kmu1 l z6i78qf sf2olng the Sun. How large an area is required to supply the needs of a house that requires $22k\,Wh/day$ Would this fit on the roof of an average house? (Assume the Sun shines about $9h/day$)   $m^2$

  Energy may be stored for use during 3lf m j8qx sq; gyrs):+yf.t1oi9mdc0peak demand by pumping water to a high reservoir whrf+s:c )f1q9msx8y .3d0 mylot;qgij en demand is low and then releasing it to drive turbines when needed. Suppose water is pumped to a lake 135 m above the turbines at a rate of $ 1.00\times10^{ 5}kg/s$ for 10.0 h at night.
(a) How much energy (kWh) is needed to do this each night?    $\times10^{9 }W\cdot\,h$
(b) If all this energy is released during a 14-h day, at 75% efficiency, what is the average power output?    kW

  Water is stored in an artificial lake created by a dam (Fxm6 lt4 )j:rfcig. 15–27). The water depth is 45 m at the dam, and a steady flow 6x 4tlrc)f: jmrate of $35m^3/s$ is maintained through hydroelectric turbines installed near the base of the dam. How much electrical power can be produced?    $ \times10^{7 }W$

  An inventor claims to have designed and built an engine thqs sbi(sv0l5 8at produces 1.50 MW of usable wosb5ss0(8qi vlrk while taking in 3.00 MW of thermal energy at 425 K, and rejecting 1.50 MW of thermal energy at 215 K. Is there anything fishy about his claim? Explain.  ----待选择----yesno 

  When $ 5.30\times10^{ 4}J$ of heat is added to a gas enclosed in a cylinder fitted with a light frictionless piston maintained at atmospheric pressure, the volume is observed to increase from $1.9m^3$ to $4.1m^3$ Calculate
(a) the work done by the gas,    $ \times10^{5 }J$
(b) the change in internal energy of the gas.    $ \times10^{5 }J$
(c) Graph this process on a PV diagram.

  A 4-cylinder gasoline engine has an effitl zmp l69 )iakukec: ;b.9ow)ciency of 0.25 and delivers 220 J of work per cycle per cylinder. .e):9zuo ti k l9mlcbkwa;6)pWhen the engine fires at 45 cycles per second,
(a) what is the work done per second?    $ \times10^{4 }J/s$
(b) What is the total heat input per second from the fuel?    $ \times10^{5 }J/s$
(c) If the energy content of gasoline is 35 MJ per liter, how long does one liter last?    s

  A “Carnot” refrigerator (the re n46jnu7a9dx bverse of a Carnot engine) absorbs heat from the freezer comparan97u b6 jd4nxtment at a temperature of -17$^{\circ}\,C$ and exhausts it into the room at 25$^{\circ}\,C$.
(a) How much work must be done by the refrigerator to change 0.50 kg of water at 25$^{\circ}\,C$ into ice at -17$^{\circ}\,C$    $ \times10^{4 }J$
(b) If the compressor output is 210 W, what minimum time is needed to accomplish this?    s

  It has been suggested that a heat engine l: aqrq4;d98n v vyaw+could be developed that made use of the temperature difference between water at the surface of the ocean and that several hundred meters deedqw r avyvla;q9+48 n:p. In the tropics, the temperatures may be 27$^{\circ}\,C$ and 4$^{\circ}\,C$, respectively.
(a) What is the maximum efficiency such an engine could have?    %
(b) Why might such an engine be feasible in spite of the low efficiency?
(c) Can you imagine any adverse environmental effects that might occur?

  Two 1100-kg cars are traveling in opposite directions when they collide (v i-m;rdytlzee+5 bc(y2 f/h :o)wm7nmf(raand are brought to rest. Estimate thyeh+-) ( i7mtorma/zfb(ln(2 dmywvf5 e :cr; e change in entropy of the universe as a result of this collision. Assume $T\,=\,20^{\circ}\,C$    $J/K$

  A 120-g insulated aluminum cup q*v3 wt im8pahr91py0at 15$^{\circ}\,C$ is filled with 140 g of water at 50$^{\circ}\,C$. After a few minutes, equilibrium is reached.
(a) Determine the final temperature,    $^{\circ}\,C$
(b) estimate the total change in entropy.    $J/K$

  (a) What is the coefficient of performance of an idev9m 8 rerg8jvr2f 0jc*ji;u ,xal heat pump that extracts heat from * iejj,v2 08 crj rgu9r8f;vmx6$^{\circ}\,C$ air outside and deposits heat inside your house at 24$^{\circ}\,C$?   
(b) If this heat pump operates on 1200 W of electrical power, what is the maximum heat it can deliver into your house each hour?    $ \times10^{ 7}J$

  The burning of gasoline in a car e(z t; )+h2idr04wg y6ecbaxkreleases about $ 3.0\times10^{ 4}kcal/gal$ If a car averages $41km/gal$ when driving $90km/h$ which requires 25 hp, what is the efficiency of the engine under those conditions?    %

  A Carnot engine has a lower operating temp0d tjdrji0* r+1biha 8erature $T_L\,=\,20^{\circ}\,C$ and an efficiency of 30%. By how many kelvins should the high operating temperature $T_H$ be increased to achieve an efficiency of 40%?    $K$

Calculate the work done by an i cd 3-vq:u m13q. kyz0ks*,vhabqqxw2deal gas in going from state A to state C in Fig. 15–28 for each of the following processes: (q qy v-,v3:kaz*d2bx3skcu0mhw q . 1qa) ADC, (b) ABC, and (c) AC directly.

  A 33% efficient powe:g9zf7/3lkac y )mdd bvs qx+1r plant puts out 850 MW of electrical power. Cooling towers are used to take away the exhaust d9 fy7:g)l/3v1s bm cqz kx+adheat.
(a) If the air temperature is allowed to rise 7.0 $C^{\circ}\,$, estimate what volume of air $(LM^3)$ is heated per day. Will the local climate be heated significantly? $\approx$   $km^3/day$(Round to the nearest integer)
(b) If the heated air were to form a layer 200 m thick, estimate how large an area it would cover for 24 h of operation. Assume the air has density $1.2kg/m^3$ and that its specific heat is about $1.0KJ/kg\cdot\,C$ at constant pressure.    $km^2$

  Suppose a power plant delivers energy at 980 MW usinsr* *c/l.ik,.f nu)e*vfsl ugt9qga5g steam turbines. The steam goes into the turbines superheated at 625 K and deposits its unused heat in river water at 285 K. Assu,kt. f9 lqngufgus ei s)*.* r5al*vc/me that the turbine operates as an ideal Carnot engine.
(a) If the river flow rate is $37m^3/s$ estimate the average temperature increase of the river water immediately downstream from the power plant.    $C^{\circ} $
(b) What is the entropy increase per kilogram of the downstream river water in $J/kg \cdot\,K?$    $J/kg\cdot\,K$

  A 100-hp car engine operates at about 15% eff cs9c3: 1+wojtkii z/srxhi( )iw.na( 0hvo1ficiency. Assume the engine’s water temperature of 85hak(rcc/z: 11o i.+t(vn9i jfih wxo i0)ss3w$^{\circ}\,C$ is its cold-temperature (exhaust) reservoir and 495$^{\circ}\,C$ is its thermal “intake” temperature (the temperature of the exploding gas–air mixture).
(a) What is the ratio of its efficiency relative to its maximum possible (Carnot) efficiency?    %
(b) Estimate how much power (in watts) goes into moving the car, and how much heat, in joules and in kcal, is exhausted to the air in 1.0 h.P =    W $Q_L$ =    $ \times10^{ 9}J$ $Q_L$ =    $ \times10^{5 }kcal$

  An ideal gas is placed in a tall cylindrical jar of cross-seckznmzbd56hz( u8 : hr;k b,5iotional area $0.800m^2$ A frictionless 0.10-kg movable piston is placed vertically into the jar such that the piston’s weight is supported by the gas pressure in the jar. When the gas is heated (at constant pressure) from 25$^{\circ}\,C$ to 55$^{\circ}\,C$, the piston rises 1.0 cm. How much heat was required for this process? Assume atmospheric pressure outside.    $J$

  Metabolizing 1.0 kg of fat :len twhjq- 0yli;4t4results in about $ 3.7\times10^{7 }J$ of internal energy in the body.
(a) In one day, how much fat does the body burn to maintain the body temperature of a person staying in bed and metabolizing at an average rate of 95 W? $\approx$ =    $kg/d$(retain two decimal places)
(b) How long would it take to burn 1.0-kg of fat this way assuming there is no food intake?    d

  An ideal air conditioner keeps the temperature inside a roomoybo(tq4x 9gle(s ejbx:4) x7 at 21$^{\circ}\,C$ when the outside temperature is 32$^{\circ}\,C$. If 5.3 kW of power enters a room through the windows in the form of direct radiation from the Sun, how much electrical power would be saved if the windows were shaded so that the amount of radiation were reduced to 500 W?    W

  A dehumidifier is essentially a “refrigerator with an open door.” The humi*dh0twj :b4 kem*hem 61c z4ced air is pulled in by a fan and guided to a cold coil, where the temperature is less than the dew point, and some of the air’s water condenses. After this water is extracted, the air is warmed back to its original temperature and sent into the room. In a well-designed dehumidifier, the heat is exchanged between the incoming and outgoing air. This way the heat that is removed by the refrigerator coil mostly comes from the condensation of water vapor to liquid. Estimate how much water is removed in 1.0 h by an ideal dehumidifier, if the temperature of the room h4 0mkce1h e6d*:ze4*bmc twjis 25$^{\circ}\,C$, the water condenses at 8$^{\circ}\,C$, and the dehumidifier does work at the rate of 600 W of electrical power.    kg