What happens to the work done when a jar of orange juice is vigoro hrf:px7t fu1w8x, e aoc(5c7lusly shaken?

When a hot object warms a cooler obvr:xf )yzg h1tq6pj(dk( *9vyject, does temperature flow between them? Are the te j((g9y: zqk6x1d)vy htvp*f rmperature changes of the two objects equal?

(a) If two objects of different te)19 dfl 9n hni3qcmah wmic/9+mperatures are placed in contact, will heat naturally flow from the object with higher internal energy to the object with lower internal energy? (b) Is it possible for heat to flow even if the internal enerfq hnmw1ci3hc9m9l ) / d+in9agies of the two objects are the same? Explain.

In warm regions where tropical plants grow f ;bex3fztx6/but the temperature may drop below freezing a few times in the winter, the destruction of sensitive plants due to freezing can be reduced by watering them in t zxfx/t;3 f6ebhe evening. Explain.

The specific heat of water is quit9xmu05+q y+j) io lbike large. Explain why this fact makes water particularly good for heatiy5 oku+)ij0i+bqlm 9 xng systems (that is, hot-water radiators).

Why does water in a metal cajjh yg tbt22z:/m*7 )(deonvr nteen stay cooler if the cloth jacket surrounding the canteen isnv72rgd )2o :(j*z j/tytm hbe kept moist?

Explain why burns caused by steam onjptmt2i1e: uuv2u 4d5 the skin are often more severe than burns caused by water u2e4 mpit5t: juvu21dat 100 $^{\circ} C$ .

Explain why water cools (its temperature drops) :h m6udb iz:y(when it evaporates, using the concepts h:z : diyb6u(mof latent heat and internal energy.

Will potatoes cook faster if the water is boiling faster(q7 7ojcy6dyk?

Does an ordinary electric faj(l.r y*0swe j+ 4 vrk1:.libnevhez+ n cool the air? Why or why not? If not, why use it?

Very high in the Earth’s atmosphere, the temperature ckx(rn1qz*8y:3hiwrlg 7jxo9 an be 700 $^{\circ} C$ . Yet an animal there would freeze to death rather than roast. Explain.

Explorers on failed Arctic expeditions have surviv*rtkjm8qg )7s uwf 8m0qtt k-n5j w;(oed by covering themselves with5* )jtqn7uwk8kt(8ts-m ;morg0 qwjf snow. Why would they do that?

Why is wet sand at the beach cooler to walk on than dry sand?3s4vp w9tv:z 1a+s7s5krzw eg

If you hear that an object has “high heat lb2oy ou.yipm (*u7 1xcontent,” does that mean that its temperature is high? Explain ylu(7pbouyix* 1 .om2.

When hot-air furnaces are used to heat a house, why is it important tha syvr5bo z355at there be a vent for air to return ta5b3 yvz 5ros5o the furnace? What happens if this vent is blocked by a bookcase?

Ceiling fans are sometimes reversible, so that they drive the air d )s n68f/vmuzuown in one season and pull it zs)muv u/nf8 6up in another season. Which way should you set the fan for summer? For winter?

Down sleeping bags and parkas are often specified as ug5g +nnxt ot4ceu2(-so many inches or centimeters of loft, the actual thickness of the garment when itt eotu(2 x4n+ggcn 5-u is fluffed up. Explain.

Microprocessor chips have a “heat sink” glued on top ksf4 *-v9i a:te k f: vdy+ajp;6sy0rrthat looks like a series of fins. Why is it shaped lar rfv: vse; :y yi-*kj94stk+0pdf 6aike that?

Sea breezes are often encountered on su5k.8v8lmnd3 hefgt 9 rnny days at the shore of a large body of water. Explain in light of the fact that the temperature of the land rises more rapidly than td8h3f tngkl re58m9 v.hat of the nearby water.

The floor of a house on a foundation under which the air can flojd(u- twjiu3thk-;j ) w -n3xaw is often cooler than a floor that rests directly on the ground (such as a concrete slab fou -iw--u; jt dw)uxn3hj(3jtakndation). Explain.

A 22 $^{\circ} C$ day is warm, while a swimming pool at $22\; ^{\circ}C$ feels cool. Why?

Explain why air tempe:7f2z 4j:zx y uva6xdsrature readings are always taken with the thermometer in theu:7zd4yx fx6vz :sj 2a shade.

A premature baby in anfgl .i , g6+at.h 3h5o rjv hg,g-sbo/z/iix5m incubator can be dangerously cooled even when the air temperature in the incubator l, gv-goi+ ba igfh6//thr.3.g5j x zmisoh5,is warm. Explain.

Why is the liner of a thermos bottle silvered (F,. i2gy+wku tnh2h7pgig. 14–15), and why does it have a vacuum be7t i 2y.hnh+,2upg wkgtween its two walls?

Imagine you have a wall that is very well insulated — it has a very high thermal*o:rym-,up* )n aqld e r,l:napm*yedo-u q )r *esistance, $R_1$ Now you place a window in the wall that has a relatively low R-value, $R_2$ What has happened to the overall R-value of the wall plus window, compared to $R_1$ and $R_2$ [Hint: The temperature difference across the wall is still the same everywhere.]

Heat loss occurs through windows by the following processes: (1) ventilatidopk:rp+ 8 wi7uafo,3tmq9:h on around edges; (2) through the frame, particularly if it is metal; (3) through the glass panes; and (4) radiation. (a) For the first three, what is (are) the mechanism(s): conduction, convection, or radiatuiatp:rf7:8 h, d+kom 9q 3opwion? (b) Heavy curtains reduce which of these heat losses? Explain in detail.

A piece of wood lying in the Sun absorbs moreh w r-,+wix7ym heat than a piece of shiny metal. Yet the wood feels less hot than the metal when you pickrmxiwh7,+ y-w it up. Explain.

The Earth cools off at nighbm )*iq2c8jglt much more quickly when the weather is clear than when clou* j82lbgcm q)idy. Why?

An “emergency blanket” is a thin shiny (metal coa 6/rutk1e2e epted) plastic foil. Explain how it can help te eu/t pek216ro keep an immobile person warm.

Explain why cities situated by the ocean tend to have less extreme temperatur gm) pvekpnl8e0b4 6pa0i4f,f+a n+sqes than inlan06qps m+gn8pefbn ka4 a)4,lvfi p0+ed cities at the same latitude.

  How much heat (in joules) is required to raise the oj2;2ug+ai r rtemperature of 30.0 kg of water o+a2gur2j;ri from 15 $^{\circ} C$ to 95 $^{\circ} C$ ?    $ \times10^{7 }\,J$

  To what temperature will 7700 J of heat raise 3.0 kg of water o6w2k5kh ;mtpi.leztd4,h/a that is initially at 10,2m 6 heptkd5 4/alkw.zo i;th.0 $^{\circ} C$ ?    $^{\circ} C$

  An average active person c zgk72gyw0gpeuf/t0 g ; 2b0peonsumes about 2500 Cal a day.
(a) What is this in joules?   $ \times10^{7 }\,J$
(b) What is this in kilowatt-hours?    kWh
(c) Your power company charges about a dime per kilowatt-hour. How much would your energy cost per day if you bought it from the power company? Could you feed yourself on this much money per day?    dollars per day

A British thermal unit (Btu) is a unit of n: jmreqpy:* 0i5c/a 9;rkfoqheat in the British system of units. One Btu is defined as the heat needef*0ji9p mn:5q;kyc /roraq:ed to raise 1 lb of water by 1 F $^{\circ} $ . Show that
1Btu = 0.252kcal=1055J

  A water heater can generaxxt/r w ((bq/y0+tou /k ,fhoqte $32,000\,kJ/h$ How much water can it heat from 15 $^{\circ} C$ to 50 $^{\circ} C$ per hour?    kg/h

  A small immersion heater is rated at snw 6 htmc.wc-td,i3,350 W. Estimate how long it will take to heat a ccnthstw .6 3mwc- d,i,up of soup (assume this is 250 mL of water) from 20$^{\circ} C$ to 60$^{\circ} C$ .    min

  How many kilocalories are generated when n /syf eupeo*r798y.z ,fe4 (of 7v8mumkmul+ the brakes are used to bring a 1200-kg coe. mk9rp(7s/u4 eyu788vz yfo,lfn uf+me *mar to rest from a speed of $95\,km/h$ ?    kcal

  An automobile cooling mmc zrh33i2zrl duw )*;m+h+e system holds 16 L of water. How much heat does it absorb i+ d3 hz cwu )ir3zl+2r*;emmhmf its temperature rises from 20$^{\circ}C $ to 90$^{\circ} C$?    $ \times10^{ 6}\,J$

  What is the specific heat of a metal substance if 135 kJ of heat is1 -kbh 5, /yl:bcfq7oin j-rek needed to raise 5.1 kg of the mete yk ,1bq-h7cofrjk n-ib/l5:al from 18.0$^{\circ}C $ to 31.5$^{\circ} C$ ?    $J/kg\cdot\,C^{\circ} $

  Samples of copper, aluminum, and tqnzzxfw (824 water experience the same temperature rise when they absorb thex( z2fwtq48z n same amount of heat. What is the ratio of their masses? [Hint: See Table 14–1.]$m_{Cu}$ : $m_{Al}$ : $m_{H_2O}$ =    :    :   

  A 35-g glass thermome(h9zum onck-1a lf +h7ter reads 21.6$^{\circ} C$ before it is placed in 135 mL of water. When the water and thermometer come to equilibrium, the thermometer reads 39.2$^{\circ} C$ . What was the original temperature of the water?$T_{iH_2O}$ =    $^{\circ}C $

  What will be the equilibrium temperature when a2 8f7gp lhtu2u 245-g block of copper at 285$^{\circ}C $ is placed in a 145-g aluminum calorimeter cup containing 825 g of water at 12.0$^{\circ} C$ ? $T_{eq}$ =    $^{\circ} C$

  A hot iron horseshoe (masl6 a uschiwsyc(knq7+97 l(/xyg+t 4ws = $0.4\,kg$) just forged (Fig. 14–16), is dropped into 1.35 L of water in a 0.30-kg iron pot initially at 20.0$^{\circ} C$ . If the final equilibrium temperature is 25.0$^{\circ} C$, estimate the initial temperature of the hot horseshoe.    $^{\circ} C$

  A 215-g sample of a substance is xi * k1luo zyvmo0.3tjjq0+z)heated to 330$^{\circ} C$ and then plunged into a 105-g aluminum calorimeter cup containing 165 g of water and a 17-g glass thermometer at 12.5$^{\circ} C$ . The final temperature is 35.0$^{\circ} C$ . What is the specific heat of the substance? (Assume no water boils away.)    $J/kg \cdot C^{\circ} $

  How long does it take a 750-W coffeepot to bring to a boi0y bur4cc5vnd2w xr 59l 0.75 L of water initially at 8.yv b c0w5r 95rdn4cux20$^{\circ}C$? Assume that the part of the pot which is heated with the water is made of 360 g of aluminum, and that no water boils away. $\approx$    min (Round to the nearest integer)

  Estimate the Calorie content of 75 g r0cp ksf0-0n-wc q:weof candy from the following measurements. A 15-g sample of the candy is allowed to dry before putting it in a bomb calorimeter. The aluminum bomb has kw:fsc-cprq0 w0-0e na mass of 0.725 kg and is placed in 2.00 kg of water contained in an aluminum calorimeter cup of mass 0.624 kg. The initial temperature of the mixture is 15.0$^{\circ}C $ , and its temperature after ignition is 53.5$^{\circ} C$ .    Cal

  When a 290-g piece of iron2.yyjsmx f f w2qzw17eh a5e06*hvwn( at 180$^{\circ} C$ is placed in a 95-g aluminum calorimeter cup containing 250 g of glycerin at 10$^{\circ} C$ , the final temperature is observed to be 38$^{\circ}C $ . Estimate the specific heat of glycerin.    $J/kg \cdot C^{\circ} $

  The 1.20-kg head of a hammer has a speicb1 p/kj9h6yv-nj 6 hed of $6.5\,m/s$ just before it strikes a nail (Fig. 14–17) and is brought to rest. Estimate the temperature rise of a 14-g iron nail generated by 10 such hammer blows done in quick succession. Assume the nail absorbs all the energy.    $C^{\circ} $

  The heat capacity, C, of an objeclxu1xo3xiggfaj6 -oe+3t. nf7 10 sjht is defined as the amount of heat needed to raise 6xf- 1uagxo+oflejt sx3gi h3n.710jits temperature by 1 $C^{\circ} $ . Thus, to raise the temperature by $\Delta\,T$ requires heat Q given by
$Q\,=\,C\,\Delta T$
(a) Write the heat capacity C in terms of the specific heat, c, of the material.
(b) What is the heat capacity of 1.0 kg of water?    $ \times10^{3 }\,J/C^{\circ}$
(c) Of 25 kg of water?   $ \times10^{ 5}\,J/C^{\circ}$

  How much heat is needed to melt 16.50 kg of silver that is initially at 2 x3.hlmb s2s6y0$^{\circ} C$?    $ \times10^{6 }\,J$

  A 0.095-kg aluminium sphere is dropped from the roof of e05 rha7c4zgk *vdc,6;dbd+7zrhyima 45-m-high building. If 65% of th7e zzd7i gd 0;, dkc65c+brryva4hh*me thermal energy produced when it hits the ground is absorbed by the sphere, what is its temperature increase?    $C^{\circ}$

  During exercise, a person may give off 180 kcal of heat in 30 min by evaporatid, ( ,(dtddq* anyk7iton of water from the skin. How much watktd y(n(*q ,dda 7,diter has been lost?    kg

  If $2.80 \times10^{ 5}J$ of energy is supplied to a flask of liquid oxygen at -183$^{\circ} C$ how much oxygen can evaporate?    kg

  A 30-g ice cube at its melting point is dropped g 88xf:zyusf ss l57t,lc0(lainto an insulated container of liquid nitrogen. How much ni ac:ls(0ul 5s xzy8fslg7t,f8 trogen evaporates if it is at its boiling point of 77 K and has a latent heat of vaporization of $200\,kJ/kg$ Assume for simplicity that the specific heat of ice is a constant and is equal to its value near its melting point.    kg

  A cube of ice is taken from the freezer at z: q(gppp*n3n -8.5 $^{\circ} C$ and placed in a 95-g aluminum calorimeter filled with 310 g of water at room temperature of 20.0$^{\circ} C$. The final situation is observed to be all water at 17.0$^{\circ} C$. What was the mass of the ice cube?    $ \times10^{-3 }$ kg

  An iron boiler of mass 230 kg contains 830 kg oukg *n5p wxe5/ o74n v+to,iykf water at 18$^{\circ} C$. A heater supplies energy at the rate of $52,000\,kJ/h$ How long does it take for the water
(a) to reach the boiling point,$\approx$    h (Round to one decimal place)
(b) to all have changed to steam?$\approx$    h (Round to the nearest integer)

  In a hot day’s race,8te h:u:iwe;anl m.( x a bicyclist consumes 8.0 L of water over the span of four hours. Making the approximation that all of the cyclist’s energy goes into evaporating this water as sweat, how much energy inx8eute; whma li (n::. kcal did the rider use during the ride? (Since the efficiency of the rider is only about 20%, most of the energy consumed does go to heat, so our approximation is not far off.)    kcal

  What mass of steam at 10s7in35 .pu mcs 1sqydaq0ljz1.+a (sc 0$^{\circ} C$ must be added to 1.00 kg of ice at 0$^{\circ} C$ to yield liquid water at 20$^{\circ} C$ ?    kg

  The specific heat of mer,p9+v0az yh40z ( zfzv wv;4 k)xugebecury is $138\,J/kg$$\cdot\,C$ Determine the latent heat of fusion of mercury using the following calorimeter data: 1.00 kg of solid Hg at its melting point of -3.9$^{\circ} C$ is placed in a 0.620-kg aluminum calorimeter with 0.400 kg of water at 12.80$^{\circ} C$ ; the resulting equilibrium temperature is 5.06$^{\circ} C$ .    $ \times10^{ 4}$ J/kg

  A 70-g bullet travelq1w 9 )w,yd+gb1q xl l-w4uszling at $250\,m/s$ penetrates a block of ice at 0$^{\circ} C$ and comes to rest within the ice. Assuming that the temperature of the bullet doesn’t change appreciably, how much ice is melted as a result of the collision?   g

  A 54.0-kg ice-skater moving *92kfusyga n96 uaw r-at $6.4\,m/s$ glides to a stop. Assuming the ice is at 0$^{\circ} C$ and that 50% of the heat generated by friction is absorbed by the ice, how much ice melts?    g

  At a crime scene, the forensi-u xlgaw,4ql.rcwebj . 0h5 al2f4g;kc investigator notes that the 8.2-g lead bullet that was stopped in a doorframh 0. q 24wxk l-u gjarecl.agb45,lfw;e apparently melted completely on impact. Assuming the bullet was fired at room temperature (20$^{\circ} C$ ), what does the investigator calculate as the minimum muzzle velocity of the gun?    m/s

  One end of a 33-cm-long aluminum rod with a diameter ofg+ ar o 0edlvm e:8(10.skotwq 2.0 cm is kept at 460$^{\circ} C$ , and the other is immersed in water at 22$^{\circ} C$ . Calculate the heat conduction rate along the rod.    W

  Calculate the rate of heat flow by conduction in Example 14–10, assuming that j e+ho9gw*y;rthere are strong gusty winds and the external ew9*jyg+ ;rho temperature is -5$^{\circ} C$   $ \times10^{4 }$ W

  (a) How much power is radiate6s3j3 k :gzhi w:;4x p-qse7ruqc.o vnd by a tungsten sphere (emissivity $e\,=\,0.35$) of radius 22 cm at a temperature of 25$^{\circ} C$ ?    W
(b) If the sphere is enclosed in a room whose walls are kept at -5$^{\circ} C$ what is the net flow rate of energy out of the sphere?    W

  Heat conduction to skin. Supr5yz b.p,7groey4lij+:4zte 0of w j,pose 200 W of heat flows by conduction from the blood capillaries beneath yor,+ ,zftwz . lep4j75 or:i40eygb jthe skin to the body’s surface area of $1.5\,m^2$ If the temperature difference is 0.50 $C^{\circ} $ , estimate the average distance of capillaries below the skin surface.    $ \times10^{-4 }$ m

  Two rooms, each a cube 4.gm qthzzwx,,2h00c i1 0 m per side, share a 12-cm-thick brick wall. Because of a number of 100-W lightbulbs in one room, the axwi 0qhzhm1t0,c2 gz,ir is at 30$^{\circ} C$, while in the other room it is at 10$^{\circ}C $. How many of the 100-W bulbs are needed to maintain the temperature difference across the wall?    bulbs

  How long does it take the Sun to melt a s/(fm(e vv:xj block of ice at 0$^{\circ} C$ with a flat horizontal area $1.0\,m^2$ and thickness 1.0 cm? Assume that the Sun’s rays make an angle of 30$^{\circ} $ with the vertical and that the emissivity of ice is 0.050.    h

  A copper rod and an aluminum rod of the sa9159 -jv udsrgv9r fteme length and cross-sectional area are attached end to end (Fig. 14–s5v 1td9ujg9fe9r v-r18). The copper end is placed in a furnace maintained at a constant temperature of 250$^{\circ} C$. The aluminum end is placed in an ice bath held at constant temperature of 0.0$^{\circ} C$ . Calculate the temperature at the point where the two rods are joined.    $^{\circ} C$

  (a) Using the solar constant, estimate the rate at which the whole Ear*92iwzzh6pgehv 5u oakj )- l4th receives energy f) 2 wuhp go zlzai*k6-h9ev4j5rom the Sun.    $ \times10^{17 }$W
(b) Assume the Earth radiates an equal amount back into space (that is, the Earth is in equilibrium). Then, assuming the Earth is a perfect emitter ($e\,=\,1.0$) estimate its average surface temperature.    $^{\circ} C$

  A 100-W lightbulb generates 95 W of heat, which is dissipated throuw +kqtkq+u*n ;gh a glass bulb that has a radius of 3.0 cm and is 1.0 mm thick. What is the difference in temperature between thenk+ ;w+ qqtk*u inner and outer surfaces of the glass?   $^{\circ}C $

  Suppose the insulating qualities of the wall of a house come mainiws:6c-sdpwwu0 -e1zl vx14l t ,9cr ply from a 4.0-in. layer of brick and an R-19 layer of insulation, as shown in Fig. 14–19. What is the totalws-1ul6wisrp:pl xc4-ezw10,vd t9 c rate of heat loss through such a wall, if its total area is $240ft^2$ and the temperature difference across it is 12 $F^{\circ} $?    Btu/h

A double-glazed window has two panes of glass separated by an air space, apy)vu )b2v/a Fig. 14–20. (a) Show that the rate of heat flow through such a window by conduction is given by/) apv)u2yabv
$\frac{Q}{t}$ = $\frac{A(T_2-T_1)}{l_2/k_1+l_2/k_2+l_3/k_3}$,
where $k_1$,$k_2$ and $k_3$ are the thermal conductivities for glass, air, and glass, respectively. (b) Generalize this expression for any number of materials placed next to one another.

  Approximately how long should it t 89 ;v,pd*, 3jlgl4+ijjgk qdamkc2vqake 11.0 kg of ice at 0$^{\circ}C $ to melt when it is placed in a carefully sealed Styrofoam ice chest of dimensions $25\,cm\times\,35\,cm\times\,55\,cm$ whose walls are 1.5 cm thick? Assume that the conductivity of Styrofoam is double that of air and that the outside temperature is 32$^{\circ} C$.    $ \times10^{4 }$s

  A soft-drink can conta)wvfqg+x,f)m ins about 0.20 kg of liquid at 5$^{\circ}C $. Drinking this liquid can actually consume some of the fat in the body, since energy is needed to warm the water to body temperature (37$^{\circ} C$). How many food Calories should the drink have so that it is in perfect balance with the heat needed to warm the liquid?    C

  If coal gives off $30\,MJ/kg$ when it is burned, how much coal would be needed to heat a house that requires $ 2.0\times10^{5 }\,MJ$ for the whole winter? Assume that 30% of the heat is lost up the chimney.    kg

  To get an idea of how much e ;h:i57 oqlf26fl qdgthermal energy is contained in the world’s oceans, estimate th;: d6qffge2 7llqio5he heat liberated when a cube of ocean water, 1 km on each side, is cooled by 1 K. (Approximate the ocean water as pure water for this estimate.)    $ \times10^{ 15}\,J$

  A 15-g lead bullet is tested by firing it into ae:mg+ v*sww *u fixed block of wood with a mass+:v *s gmwwue* of 1.05 kg. The block and imbedded bullet together absorb all the heat generated. After thermal equilibrium has been reached, the system has a temperature rise measured as 0.020 $C^{\circ} $. Estimate the entering speed of the bullet.    m/s

  (a) Find the total power radiated into space6xc fad2-oc3 a by the Sun, assuming it to be a perfect emitterfcoa2- d36ca x at $T\,=\,5500K$ The Sun’s radius is $7.0 \times10^{ 8}\,m$    $ \times10^{ 26}\,W$
(b) From this, determine the power per unit area arriving at the Earth, $1.5 \times10^{ 11}\,m$ away (Fig. 14–21).    $ \times10^{ 3}\,W/m^2$

  During light activity, ag mp /0jr;,:umlvpo6 y 70-kg person may generate $200kcal/h$ Assuming that 20% of this goes into useful work and the other 80% is converted to heat, calculate the temperature rise of the body after 1.00 h if none of this heat were transferred to the environment.    $C^{\circ} $

  A 340-kg marble boulder rolls off the-nnz oy0vnkyv*9,(l;uz:lap top of a cliff and falls a vertical height of 140 m before striking the ground. Estimate the temperature ris oypvzu:lln0-ky nz9vn (,;a *e of the rock if 50% of the heat generated remains in the rock.    $C^{\circ} $

  A 2.3-kg lead ball isr-p mi*q : hgz+ev j/rvmu()d7 dropped into a 2.5-L insulated pail of water initially at 20.0u/ -d7pg:m(ev)z+v hr *q mijr$^{\circ} C$. If the final temperature of the water–lead combination is 28.0$^{\circ} C$, what was the initial temperature of the lead ball?    $^{\circ}C $

  A mountain climber wed9 smbr+.(dk vq5j6c) py ou(a22vxibars a goose down jacket 3.5 cm thick with total surface area i.b (yu5ros m vadv6qb dp2+(c9j)2kx$1.2\,m^2$ The temperature at the surface of the clothing is -20$^{\circ}C $ and at the skin is 34$^{\circ} C$. Determine the rate of heat flow by conduction through the jacket
(a) assuming it is dry and the thermal conductivity k is that of down,    W
(b) assuming the jacket is wet, so k is that of water and the jacket has matted to 0.50 cm thickness.    W

  A marathon runner has an hd) wz(fh7 o2maverage metabolism rate of about $950\,kcal/h$ during a race. If the runner has a mass of 55 kg, estimate how much water she would lose to evaporation from the skin for a race that lasts 2.5 h.    kg

  Estimate the rate at which heat can be conducteotrh / f.y9x-fd from the interior of the body to the surface. Assume that the thickness of tissue is 4.0 cm, that the skin is x .fo f/9-ryhtat 34$^{\circ}C $ and the interior at 37$^{\circ}C $, and that the surface area is $1.5\,m^2$ Compare this to the measured value of about 230 W that must be dissipated by a person working lightly. This clearly shows the necessity of convective cooling by the blood.    W

  A house has well-insulated walls 17.5 cm thick (assume conductivity of air) andt c,3n8x r ta9bekuorpu8:/ +h are,/:rturhnukoe+at88xc p93b a $410\,m^2$ a roof of wood 6.5 cm thick and area $280\,m^2$ and uncovered windows 0.65 cm thick and total area $33\,m^2$
(a) Assuming that heat is lost only by conduction, calculate the rate at which heat must be supplied to this house to maintain its inside temperature at 23$^{\circ}C $ if the outside temperature is -10$^{\circ} C$    $ \times10^{5 }$W
(b) If the house is initially at 10$^{\circ} C$, estimate how much heat must be supplied to raise the temperature to 23$^{\circ} C$ within 30 min. Assume that only the air needs to be heated and that its volume is $750\,m^3$    $ \times10^{ 8}$J
(c) If natural gas costs 0.080 dollars per kilogram and its heat of combustion is $ 5.4\times10^{7 }\,J/kg$ how much is the monthly cost to maintain the house as in part (a) for 24 h each day, assuming 90% of the heat produced is used to heat the house? Take the specific heat of air to be $0.24\,kcal/kg$$\cdot\,C$.    dollars

  A 15-g lead bullet travq )g491utddbceling at $220\,m/s$ passes through a thin wall and emerges at a speed of $160\,m/s$ If the bullet absorbs 50% of the heat generated, (a) what will be the temperature rise of the bullet? (b) If the bullet’s initial temperature was 20$^{\circ} C$, will any of the bullet melt, and if so, how much?    $C^{\circ} $

  A leaf of area $40\,cm^2$ and mass $ 4.5\times10^{-4 }\,kg$ directly faces the Sun on a clear day. The leaf has an emissivity of 0.85 and a specific heat of $0.80\,kcal/kg\,\cdot K$.
(a) Estimate the rate of rise of the leaf’s temperature.    $C^{\circ} $
(b) Calculate the temperature the leaf would reach if it lost all its heat by radiation to the surroundings at 20$^{\circ} $C.    $^{\circ}C $
(c) In what other ways can the heat be dissipated by the leaf?

  Using the result of part (a) in Problem 5,4az dgnz+nyqj( 7x ty+,5ldo 8, take into account radiation from the leaf to calculate how mucztg4 +( 7+yxna,,qdzl 5 doyjnh water must be transpired (evaporated) by the leaf per hour to maintain a temperature of 35$^{\circ} C$.    g/h

  An iron meteorite melts when i2mhn;2, i0d nd- gjjxvl4o;zo t enters the Earth’s atmosphere. If its initial tem;m0gn ;jo4dl 2jn ho2i ,vxd-zperature was -125$^{\circ} C$ outside of Earth’s atmosphere, calculate the minimum velocity the meteorite must have had before it entered Earth’s atmosphere.    m/s

  The temperature within the Earth’s crust increases aboum 2w8kjn kfx0.t 1.0 C$^{\circ} $ for each 30 m of depth. The thermal conductivity of the crust is $0.80\,W/C^{\circ} \cdot\,m$
(a) Determine the heat transferred from the interior to the surface for the entire Earth in 1 day.    $ \times10^{18 }\,J$
(b) Compare this heat to the amount of energy incident on the Earth in 1 day due to radiation from the Sun.$Q_{Sun}$ =    $ \times10^{4 }\,Q_{interior}$

  In a typical game of squasf )put6jz ulwv(, 0v v.ck6-yoh (Fig. 14–22), two people hit a soft rubber ball at a wall untiu6)v tzuv0v l(wy,kpf- cj6.o l they are about to drop due to dehydration and exhaustion. Assume that the ball hits the wall at a velocity of $22\,m/s$ and bounces back with a velocity of $12\,m/s$ and that the kinetic energy lost in the process heats the ball. What will be the temperature increase of the ball after one bounce? (The specific heat of rubber is about $1200\,J/kg\,$$\cdot\,C$)    $C^{\circ} $

What will be the final result when equal 1 )fib cocve5umel,-0kfm++w masses of ice at 0$^{\circ} C$ and steam at 100$^{\circ}C $ are mixed together?

  In a cold environment, a person can lose heat by conduction and radiatisi6n8attk/; v1u re u:w :xx7kon at a rate of about 200 W. Estimate how long it would take for the body temper6wse tuxiv:k 1tn/8:rax ;ku7ature to drop from 36.6$^{\circ} C$ to 35.6$^{\circ} C$ if metabolism were nearly to stop. Assume a mass of 70 kg. (See Table 14–1.)    s

  After a hot shower and dishwashing, there is “no hkch +( p;0jrkmot water” left in the 50-gal (185-L) wkj(hk c0+p ;rmater heater. This suggests that the tank has emptied and refilled with water at roughly 10$^{\circ} C$. (a) How much energy does it take to reheat the water to 50$^{\circ} C$? (b) How long would it take if the heater output is 9500 W?    s

  The temperature of the glass surfuhj1 -st;yj1jc)v6r hace of a 60-W lightbulb is 65$^{\circ} C$ when the room temperature is 18$^{\circ} $C. Estimate the temperature of a 150-W lightbulb with a glass bulb the same size. Consider only radiation, and assume that 90% of the energy is emitted as heat.    $^{\circ} C$