What happens to the work done when a jar of oragtknx +3+r:s j ppuebkh,-v 5/nge juice is vigorously shaken?

When a hot object warms a cooler object, does temperature flow betwexez.7usale4 xk9 t 9u2z6h1oaen them? Are the temperature changes of the two obj2xu1ozxuel 49 a69eksha tz7.ects equal?

(a) If two objects of differentw-+plgyt h9/8 7cox;0bndbxd temperatures 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 possibyddbg+/7xt-w 0 l 9noxcp;h 8ble for heat to flow even if the internal energies of the two objects are the same? Explain.

In warm regions where tropical plants grow but the temper/6xjrd3gnuh,z a)+kp8 p .la eature may drop below freezing a few times in the winter, the destructionk jph,ngr z/+6ulx3 d epa).8a of sensitive plants due to freezing can be reduced by watering them in the evening. Explain.

The specific heat of water is quite large. Explain why zfu3ar qb. :5t+/dkf gthis fact makes water particularly good for heating 3zqa ft fu+5d.bgk /r:systems (that is, hot-water radiators).

Why does water in a metal canteen stay cooler if the re gs*hb3s564 3gzu cqcloth jacket surrounding the cauq3sch*4gsr 3g5z 6eb nteen is kept moist?

Explain why burns caused by /-yme/09c jmisvj y1o steam on the skin are often more severe than burns caus y9yemi-/jcovm0s /j1ed by water at 100 $^{\circ} C$ .

Explain why water cools (its 2flr9vdlc0xn 9( qs*ftemperature drops) when it evaporates, using the concepts cdn2*9r v0 xslfq(lf9 of latent heat and internal energy.

Will potatoes cook faster if the water is baqmwj tc +33f4oiling faster?

Does an ordinary electric fan cool the air? Why or why not? If noi7yenr/wz .t.n sip/ -*ejy r0t, why use it?

Very high in the Earth’s atmosphere, th q8 bphkoq9ypf9ldk21l4j xt,37f x/ 4z+dvrwe temperature can be 700 $^{\circ} C$ . Yet an animal there would freeze to death rather than roast. Explain.

Explorers on failed 7lh** +1jr obdkcxzrvz) 1a2cArctic expeditions have survived by covering themselves with snow. Why woulb2)17 vzl1rdz c*+a x*jhrkocd they do that?

Why is wet sand at the beach cooler to walk on tydp(,,xb5byz era 1r* han dry sand?

If you hear that an object has “high heat content,” does that mr3ih6)i wa7nat;pcp: ean that its temperatun;7t pr6w3c )hiia :pare is high? Explain.

When hot-air furnaces are used to heat a house,rp tx)p-n53l h 8zgwc 9q4sub9 why is it important that there be a vent for air t3pt5g-)8xclu4bp z rwq n9h s9o return to the furnace? What happens if this vent is blocked by a bookcase?

Ceiling fans are someti 0schd3w2um1t mes reversible, so that they drive the air down in one season and puc0hu s3d 12wmtll it up in another season. Which way should you set the fan for summer? For winter?

Down sleeping bags and parkas are often specified asg hcnwzv1- p 3i(pn4xkhp9+-n so many inches or centimeters of loft, the actual thickness of the garment when itn1- ipwcxpp(v39n4-+zhhgn k is fluffed up. Explain.

Microprocessor chips have a “heat sink” glued on top that looks like a series of lozq6tgxvnbuhq;b09 + v ;/y9 fins. Why is itobng6yu/9vqq bx;0 z9+vlt ;h shaped like that?

Sea breezes are often encountered on sunny days at the shon1mptnlim;y /.yg4: wyxf,: are of a large body of water. Explain in light of the fact that the temperature of the land rises more rapidly than that of mfm tn ,lx4 1;ni/.y:wapyyg:the nearby water.

The floor of a house on a foundation under which the air can flow is often4q29qddd . ykd cooler than a d 9ydqq2kd.d4 floor that rests directly on the ground (such as a concrete slab foundation). Explain.

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

Explain why air temperature reading9y gzk +tq/dx;s are always taken with the thermometer in the shadedx+g 9/tykq; z.

A premature baby in an incubator can be dangerously cowgc :ue 3sv0or;)a*h soled even when the air temperature in the incubator ih:u3) o0gess;cawvr * s warm. Explain.

Why is the liner of a thermos bottle silvered (Fig.9s9saejeu*ubzr -mh52my85 n 14–15), and why does it have a vacuum between its twsr9ez58ms m5 2hj-ean 9yu* ubo walls?

Imagine you have a wall that is very well insulated — it hrwz 6s9k5c +izas a very high thermal resistac 5s9z6 +rkiwznce, $R_1$ 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 wia34bip0b/n so;pb0rj (;mim+o ma 8umndows by the following processes: (1) ventilation around edges; (2) through the frame, particularly if it is metal; (3) through the glass panes; and (4) radiation. (a) Fo8ba 40;mbm j mbp(mn io;i30sora +p/ur the first three, what is (are) the mechanism(s): conduction, convection, or radiation? (b) Heavy curtains reduce which of these heat losses? Explain in detail.

A piece of wood lying in the Sun absorbs more heat than a pa /fy cxd5gc,;iece of shiny metal. Yet the wood feels less hot than the metal wh,c/dgf5 a;xyc en you pick it up. Explain.

The Earth cools off at night much more kh3.3xjb2qfh quickly when the weather is clear than when cloudy. Why2jfh 3xq3bh k.?

An “emergency blanket” is a thin shiny (metal coated) plabi9a02)lq oq 8xo4yj69zx yr(w jdq ,zstic foil. Explain how itzaxi q29j0o( 6yyr qd xo,j8zbl)q4w9 can help to keep an immobile person warm.

Explain why cities situated by the ocean tend to have less es5n ,axk+*tgaxtreme temperatures than inland cities at the same lat* tsnxgka5a,+ itude.

  How much heat (in joule86.gtno eca6tntt7c0 wz .cx/s) is required to raise the temperature of 30.0 kg of water from 1cx8/t azoc 0wt.6et.c7 g6tnn 5 $^{\circ} C$ to 95 $^{\circ} C$ ?    $ \times10^{7 }\,J$

  To what temperature will 7700 J of heat raise 3.0 kg of water that is in6l q*qj6u3vf-tu,z lbitially at 10.b3fq*6z jtu -ul,l 6vq0 $^{\circ} C$ ?    $^{\circ} C$

  An average active pe 4j7e 6sk h +aeh)1j:oij;kjxnrson consumes 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 heat in the British system of ly reudy j7n)pq /;4i4units. One Btu is defined as the heat needed to q4lpiu4;ynr y dj7e /)raise 1 lb of water by 1 F $^{\circ} $ . Show that
1Btu = 0.252kcal=1055J

  A water heater can gene4p pl.7v5;iuz- e ktxp4n km:orate $32,000\,kJ/h$ 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 3abgr /xa1 *or(50 W. Estimate how long it will take to heat a cup of sgra axo* r/1(boup (assume this is 250 mL of water) from 20$^{\circ} C$ to 60$^{\circ} C$ .    min

  How many kilocalories are generated when the brakes are usedqoj lt98ecx0 b00f/ or to bring a 1200-kg car tox0oc900l8fo rejb t/q rest from a speed of $95\,km/h$ ?    kcal

  An automobile cooling system holds 16 L of water. How much heat doe9p - m3-z5yd 5y- isccahobm5ds it absorb if its temperature rises froy3sm5 zpc-h5-im9cayb dd 5o-m 20$^{\circ}C $ to 90$^{\circ} C$?    $ \times10^{ 6}\,J$

  What is the specific heat qfnq.qnr2+mi72i(ey 2t1w 8:hygj zq of a metal substance if 135 kJ of heat is needed to raise +ym2z yi 2tqnh1 ji8q 7:w.rf2(eq nqg5.1 kg of the metal from 18.0$^{\circ}C $ to 31.5$^{\circ} C$ ?    $J/kg\cdot\,C^{\circ} $

  Samples of copper, aluminum, and water experience the same temper9( -9jlniu ekiature rise when they absorb the same amount of heat. What is the ratio of their masses? [Hintkj9-n9luie( i: See Table 14–1.]$m_{Cu}$ : $m_{Al}$ : $m_{H_2O}$ =    :    :   

  A 35-g glass thermometerfzg38a.g. o xr 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 temper-r gq wec+0k6tz)2nj tature when a 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 (mass cpl68 i epq+x(p(:c aw= $0.4\,kg$) 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 is6 yog(otkz joz0yo) ;0 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 boil a28p:j(q g +vm(nj fly0.75 L of water initially fl+jqpjv8y(ma :(gn 2at 8.0$^{\circ}C$? 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 of candy from thpispzphe 9w2 30vb9b6e following measurements. A 15-g sample of the candy is allowed to dry before putting it in a bomb calorimeter. The aluminum bomb has a 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 teb6bsv2p3 i90ep wphz9mperature of the mixture is 15.0$^{\circ}C $ , and its temperature after ignition is 53.5$^{\circ} C$ .    Cal

  When a 290-g piece ofa 3sp;3jl;yxjh lf (g0 iron 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 has1q)chowxcmt 5x t 616n a speed 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 objeso(w8kmw1(fmtu7y ;t ct is defined as the amount of heat needed to raise its temperature b(ywo;s m m(fw kt7tu18y 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 y3.kll3 eim)t2uj peu ih ht:1o o+9,fsilver that is initially at 20$^{\circ} C$?    $ \times10^{6 }\,J$

  A 0.095-kg aluminium sphex9f23 kq pr6ozfr:;op re is dropped from the roof of a 45-m-high building. If 65% of the thermal energy produced when it hits the ground is absorbed by the sphere, what is its tempera3o9 ;xk2f6q rf:rpopz ture increase?    $C^{\circ}$

  During exercise, a person may giv1vt.zk 8rtax4r7h) y2 g5bzag e off 180 kcal of heat in 30 min by evaporation of water froa hr58 47ztkrtb xv.) yg1g2zam the skin. How much water 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 m0 6xf( nsojrfwi1z 0t;pp(h;l elting point is dropped into an insulated container of liquid nitrogen. How much nitrogen evapoz p tofh(;fx;ijpw0 n10s6 l(rrates 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 freezeygp2w*.lkzx 3phob-+r at -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 containscs3 ij8em+d jtg(,y7esi06kg 830 kg of 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, a bicyclitb7bdb+ 6bk-n st 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 in kcal did the rider use during the ride? (Since the efficiency of the rider is ondk b+b6bt 7b-nly about 20%, most of the energy consumed does go to heat, so our approximation is not far off.)    kcal

  What mass of steam at 100yc1*wumox/ i0 $^{\circ} C$ 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 me zcjzth tr vhqy/+j;/uq.i ()/rcury 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 traveling at44up dtsm56uihs +a g9 $250\,m/s$ 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 at 2** ozwzv2p et.8sc xd,f dn(p$6.4\,m/s$ 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 uo k3y3uiy6l(cwk1zc6(x gd*lvwm9+ forensic investigator notes that the 8.2-g lead bullet that was stopped in a doorframe apparently melted completely on impact. Ayd6gwl m(z+36 i9kcxk3 u co*lwuvy( 1ssuming 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 5 u4r-v(wb )suf8x urrof 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 i0:4wc:hxpkze k;lv -that there are strong gusty winds and the extelv-kex ;:h zwp0 i4c:krnal temperature is -5$^{\circ} C$   $ \times10^{4 }$ W

  (a) How much power is r73x19o.(gkwkiru gytadiated 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. Suppose 200 W of heat flows by czil ,t.jmo*nuk 4m8*:ra 8qlconduction from the blood capillaries beneath the skin to the body’s surface *:muknq,mlc a. * t4 zjl8ir8oarea 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 4.0 m per side, share a h1a ,du gj3(t8sj4r td12-cm-thick brick wall. Because of a number of 100-W ligh 431 sjudt d,tg8(hjratbulbs in one room, the air 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 block of ice c*/2 j-/cnvime c7 olo;es;io 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 same length and cross-section5 ,rhl7f a6yj ll z3m4g303iiv0zsnpral area are attached end to end (Fig. 14–18). The copper end is placedi3 304a5l0y3sg hfvjll7r,mpz rzi6n 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 b.6jh3ht sw 1lwhich the whole Earth receives energy fro 36bwjhslt1.h m 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 i zmgw6:5og i0W of heat, which is dissipated through a glass bulb that has a radius of 3.0 cm and is 1.0 mm thick. What is the difference in temperature between the inner and outer surfaces of g 5 0:6moiiwgzthe glass?   $^{\circ}C $

  Suppose the insulating qualities of the wall osg xgpqll.tdn.8 1. 3gf a house come mainly from a 4.0-in. layer of brick and an R-19 layer of insulation, as shown in Fig. 14–19. What is the total rate of heat loss through such a wall, if its total area igg gps 1 .tx..q8dlnl3s $240ft^2$ 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, Figwi+s bvpt6bouhw0/ +y,/ n.i;q1uxzs . 14–20. (a) Show that the rate of heat flow through such a window by conduction is givebh1bx w uni/. 0si+y/ozupwtvs+ ;6,qn by
$\frac{Q}{t}$ = $\frac{A(T_2-T_1)}{l_2/k_1+l_2/k_2+l_3/k_3}$,
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 take6fvb(u9 p n3amdzqu) 3 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 contains about 0.20 kg of liquid at 5lf q -9 mz7jrlq7zz8x5$^{\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 thermal energy is contained in the world’s otnqh/02h)zys7( ; bphtu ah kw-an ,;gceans, estimate the heat liberated when a cube of ocean water, 1 km on each side, is cooled by 1 K./tn hhau-(sbh p )zg7thw;20;qna,yk (Approximate the ocean water as pure water for this estimate.)    $ \times10^{ 15}\,J$

  A 15-g lead bullet is tested by firing it into a fixed block of wood with a mas4s 3 y5*7ffjlhh dp9tqs of 1.05 kg. The block anqfy3*5ltd 9j4 sfph 7hd 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 space by the Sun, ass 4-bk *tkzz3w -cutteso*k;. euming it to be a perfet k3ke- -.o4tu t*zkzw;ec* bsct emitter 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, a 73)hx nmcz fh,(oug0 vfq:qp -(0-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 thqvs26gkdy j- 4e top of a cliff and falls a vertical height of 140 m jv24dk6 sqyg-before striking the ground. Estimate the temperature rise of the rock if 50% of the heat generated remains in the rock.    $C^{\circ} $

  A 2.3-kg lead ball is dropped into a 2.5-L insulated pail of water is nvqfg jr bbg(,330n)-hja6wnitially at sw3() v, g36nq0jjgbafn-h br20.0$^{\circ} C$. 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 wears a goose down jacket 3.5 cm thick wi d)lg7olyic1w1x1 rx/l* hax7th total surface area/h 7o*wxixa)x1gc rl117dl l y $1.2\,m^2$ 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 average metabo37 ikqyqc,3rm lism 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 /ys ysz)8) .apnz*nf m zpn03lna7 i4tbe conducted from the interior of the body to the surface. Assume that the thickness of tissue is 4.0 cm, )f4piz) ynstz m3nz 7pann/.y80l*asthat the skin is at 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 1y(hmn/1 7h frqio5 6fmfkqz5 cm thick (assume conductivity of air) and areah5nqrof1 56mhzmf k(/y7fq i1 $410\,m^2$ 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 traveling at 0 3skh8x xzoj9$220\,m/s$ 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 58, take into account radiati c,e/9n)/)wxjqtrumd on from the leaf to calculate how much water must be transpired (evapor njw/mt9)e )rqxd ,u/cated) by the leaf per hour to maintain a temperature of 35$^{\circ} C$.    g/h

  An iron meteorite melts when it enters the Earth’s atmospherkigr/dm(.5i d+p*8 cpybr v h-e. If its initial tempe id5ycr hd 8pkrp-/*.g vmib(+rature 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 vn.cu6s: -g2oroldg.e*jxauxa +7n:o6 9gs ocrust increases about 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 squash (Fig. 14–22), two people hit a soft rubber ball l o3o2vc86bklat a wallo2638l lok cbv until 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 masses et5h/-g mdebn u6 2b7kof ice at 0$^{\circ} C$ and steam at 100$^{\circ}C $ are mixed together?

  In a cold environment, a persof1 rz-wcxj 93gn can lose heat by conduction and radiation at a rate of about 200 j xfw g3zc19r-W. Estimate how long it would take for the body temperature 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 anp74qffsv2 xre *l pjz8 yzkgp+0v+5 ;xd dishwashing, there is “no hot water” left in the 50-gal (185-L) water heater. This sugges+s *yjz 0fg7+fp xrq p8vl;zvpk4e52x ts 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 surface of a 60-W lightbt k0 )hx-;wmub-gzm9mulb 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.    $^{\circ} C$