What happens to the work done when a jar of orange juice is vigorously shakh)s/y ck. kd; ycmitx57h4gz/en?

When a hot object warms a cooler object, does temperatupiv :ai d6qe,9xvk:xzec(ow)py-*y(re flow between them? Are the tempe yv p cx)p(,k:eyqid*e oai-v:z6(x9wrature changes of the two objects equal?

(a) If two objects of different temperatures are placed in contact, will heyt m6yh qqs,3-at naturally flow fro3mshyq-qty 6 ,m 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 energies of the two objects are the same? Explain.

In warm regions where tropical plants grow but the temperaq u gv;d69jp4dv1 tl2kture 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 the evening2v1;9dl gq t64jpk udv. Explain.

The specific heat of water is quite large. Explain why this fdq )xz ;ccw552 l.fzi7g- fvgjact makes water particuldzc gq ;5 w)c2l.fj7vg zfxi-5arly good for heating systems (that is, hot-water radiators).

Why does water in a ;ue k rrhbi7+/b 6em5dmetal canteen stay cooler if the cloth jacket surrounding the canteenekbi;drm6/ehr5+bu 7 is kept moist?

Explain why burns caused by steam on the skin are often more severzyey5 me(;p2 d5t/c;qxbaopraut:+. b* mi+ ze than burns cacedi:5tb m +xyzez2*o(5/.ab t;m p;+rayup qused by water at 100 $^{\circ} C$ .

Explain why water cools (iti zk4(zk7swga 2 3qaf6nr3o r+)w nh-ys temperature drops) when it evaporates, using the concepts of latent heat and internal enerkzr7gfa3zr )( y+-o 6n2ia4 whqs3nwkgy.

Will potatoes cook faster if the water is boiling fastydq)qjsb (dvt 3 ),x0eer?

Does an ordinary electric fan cool t j5 7koxuys9f3 h4gegubh/ (-ahe air? Why or why not? If not, why use it?

Very high in the Earth’s atmosphere, thz82f4a (ybrx ee temperature can be 700 $^{\circ} C$ . Yet an animal there would freeze to death rather than roast. Explain.

Explorers on failed Arctic e.mufyio99lh6x8x i7 w xpeditions have survived by covering themselves with snow. Why wouldy9um8xo 6l fhiw. 97ix they do that?

Why is wet sand at the beach cooler to w-d/ic- bcdd p:alk on than dry sand?

If you hear that an object has “high heat content,” does that mean thatl8s qs:cs .i2u4cwh(qbl v/ 4x its temperaturb( u/s :4v2q4wscx.hql8s l ice is high? Explain.

When hot-air furnaces are used to heatm 6p, cp5+ 1dmoe0 kaveux:6ay a house, why is it important that there be a vent for air to return to the furn6,eak 0poved1 6a5:uyxm m+cpace? What happens if this vent is blocked by a bookcase?

Ceiling fans are sometimes reversible, be.a*s ii7zro7r yiut5r qh y44g41(aso that they drive the air down in one season and pull it up in another season. Which way z5.yiq7eoi(s 4hay*4 t74i garr1u rb should you set the fan for summer? For winter?

Down sleeping bags and parkas are often specified as so uj /y*1 cof*gamany inches or centimeters of loft, the actual thickness of thao j*1fy*/ ucge garment when it is fluffed up. Explain.

Microprocessor chips have a “heausj)*,6usm - rygp-l en14mptt sink” glued on top that looks like a series of fins. Why is it shaped like that 1*j-y6upu g r,4s mnslt-e)pm?

Sea breezes are often encountered on sunny days at the shore of a larges7 60ajdwf ek1 body of water. Explain in light of the fact that the temperature of the land rises more rapidly than0kfeds wj7 a16 that of the nearby water.

The floor of a house on a foundation under whict,pgf* a9pg g8bm8a7rc* q8mz:1 cujgh the air can flow is often cooler than a floor that rests direcj*g8tgq9gu *cf81mcb:,7p p m8zaargtly 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 temperatu62+b;g9u.vtr z h ztkxtgabwx, ( .nh:re readings are always taken with the thermometer in the shadebu 6nt2tag vbh9g ; xkrzh.z (:.,xt+w.

A premature baby in an incubator can be dangerous;71 nj fye(.xanyyny34xm/ coly cooled even when the air temperatu;mxce 7nafoyy( 3 jxy /nn.1y4re in the incubator is warm. Explain.

Why is the liner of a thermos bottle silvered (Fig. 14–15), and why dd /ho jz cipo/+e:ops(lpmy 71emb 64(oes it have e1e4pm(/ 7(i o/ojyzh bp:6msclo+p da vacuum between its two walls?

Imagine you have a wall that is very well insulated — 2qtk0 6p:3hjkwq4ths it has a very high thermal resistancekqs 34p h 2k:qtjh6t0w, $R_1$ 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) ventilat+ 5vumm-aj/l 6s bkb0iion around edges-bv m5i6 jl /+ba0sumk; (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 radiation? (b) Heavy curtains reduce which of these heat losses? Explain in detail.

A piece of wood lying in twb v xw4fzw.3wqq(-;n/ aw+qthe Sun absorbs more heat than a piece of shiny metal. Yet the wood feels less hot than the metal when you pick it u w f .nwt/bwa;z3-vw4+qqwqx( p. Explain.

The Earth cools off at night much more quickly when the we+aod4 x5 jkrpsi6 zfd1gl-+5hather is clear than when cloudydapg4jzl +o6r5x +- dfihs51 k. Why?

An “emergency blanket” is a thin shiny (metal coatedxro;dx ; xq wx/-mnal9 4bej9u8x-9ak) plastic foil. Explain how it can help to keep an;4 abmrn8d9 9lx 9xw-a;jkq-x/o xe ux immobile person warm.

Explain why cities situated by the ocean tend u wuma2w21f6 u f4r8mjag(q/zto have less extreme temperatures than inland cities at the same latituduqm1/gf uwu8am2z46(f r 2wa je.

  How much heat (in joules) is required to raise the 5gk(imz fa35a temperature of 30.0 kg of water from 1az3a5gik(fm 5 5 $^{\circ} C$ to 95 $^{\circ} C$ ?    $ \times10^{7 }\,J$

  To what temperature will 7700 J of heat raise 3.0 kg of wat) e kw /r+5r4 1e.vnopkhf0vbler that is initially at 10.0 r/ 4vk5 h0+ronw)e bkf.plv1e$^{\circ} C$ ?    $^{\circ} C$

  An average active person consumes about 2500 Cal a day.-ih zuht 9l +rb7ws1i1
(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 unitxej9bfc7im224o +w i x (Btu) is a unit of heat in the British system of units. One Btu is defined as the hi4xbc2 jmf 92+oe 7wixeat needed to raise 1 lb of water by 1 F $^{\circ} $ . Show that
1Btu = 0.252kcal=1055J

  A water heater can genm:zl q x lnh;i76e7j1a4 ej.xserate $32,000\,kJ/h$ 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 350 W. Esg/yssn,tx ) w)h w7(tetimate how long it will take to heat a cup of soup (assume this is 250 mL of waterget(,7st/nhws w) xy)) from 20$^{\circ} C$ to 60$^{\circ} C$ .    min

  How many kilocalories are generated when the brakes are used to britsdy* a*ta(6 ing a 1200-kg car to rest*a6d(say tit* from a speed of $95\,km/h$ ?    kcal

  An automobile cooling system holds 16qd4tf:kgua :4c :1 crh L of water. How much heat does it absorb if idk qfrg:t44:hu c1ac:ts 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 is needed tos(5n 1agykyh 4 raise 5.1 kg of1(yanhyg5 sk4 the metal from 18.0$^{\circ}C $ to 31.5$^{\circ} C$ ?    $J/kg\cdot\,C^{\circ} $

  Samples of copper, aluminum, and water expe7r uo0jfr ippv6t6t *9rience the same temperature rise when they absorb the same amount of heat. What is the ratio of their masses? [Hfjo *r 66t97vppiu t0rint: See Table 14–1.]$m_{Cu}$ : $m_{Al}$ : $m_{H_2O}$ =    :    :   

  A 35-g glass thermometer rizg 3;e9sm- h,so( zbqeads 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 a 245-g block of copper at 2) -szjvarp2u5 85$^{\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 (mav)a: pe5x46bfw n2iudss = $0.4\,kg$) 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 substanuiqtu,o:g-f pmd5 j :-v s)ja*verf 3,ce is 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 cof,a7n51 n bpdd1xvza/o feepot to bring to a boil 0.75 L of water initially a1oann 1dbx ,v5p /dz7at 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 f2cz ,styuq18content of 75 g of 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 a mass of sfc,q28 ytuz 10.725 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 iron at 180 ku2 ll: fda* orw/;wa 9+ff:1zvp-xbp$^{\circ} C$ 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 speed umda* o+j:60xbl,qxx 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 object is defined as the amount of heat needed to rhbxw67wzg +6c ea)d 7haise its temperature6wha e7wdz)x+7hbcg 6 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 td(njjis:7os 5o melt 16.50 kg of silver that is initially at 20$^{\circ} C$?    $ \times10^{6 }\,J$

  A 0.095-kg aluminium sphere is dropped from wv/4h 3d af0b-d dv.jsr 1-cvtthe roof of a 45-m-high building. If 65% of the thermal energy produced when it hits the ground is absorbed by tb-tr ajd/0 s3d vv-cf. 4w1dhvhe sphere, what is its temperature increase?    $C^{\circ}$

  During exercise, a person may give off 180 kc8e/ba x rf5 nos-;w-alal of heat in 30 min by evaporation of water from the /rox;5ws8-l- afb eanskin. 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 melting point is dropped into an insulated container ofvy64sv v6j*:6v o-lnep e5 cfz liquid nitrogen. How much nitrogen evaporates if it is at its boiling point of 77 K and has a latent heat of vapor-6lz p6 jvvy*e6ncsfo5e4v:vization 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 taki0 xor h k75f(oc:7z8v na45bniyu9wz en from the freezer 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 co(vt)v4up4 3 hbp.dajentains 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 bicyt9umb 7)itl5v clist 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 only about 20%, most of the energy consumed does go tlitt5 79bmu)vo heat, so our approximation is not far off.)    kcal

  What mass of steam at 1y+idbtkq(b6xfq ;s tzu6/bm)d) . y 3p00$^{\circ} C$ 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 meefnpg s)o:2agk- i6s+bu6.g d x3v(hurcury 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 travel gtea4 6t0tqb1t 1pma5qgt:0x ing 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 movv e6s,f6v9 xpving 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 forensic investigator notes that the 8.2-g lead ficx 91 pgi+q6bullet that was stopped in a doorficgi6xq f 9+p1rame 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 rod5e99i8 6dg5qk.lh d e7fd:gf ax/aqzp with a diameter of 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 :; *3r9ds slv1 ozsq/uh;aqfwthere are strong gusty winds and the external *ulvds 13/qasz wqo:9;r fh;stemperature is -5$^{\circ} C$   $ \times10^{4 }$ W

  (a) How much power is radiated by a tungsten s5 joawz8 i+7qiji/ yu)phere (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 fg15p0m ljc9d v/rp 2eflows by conduction from the blood capillaries beneath the skin to the bodrjf59vmpl2 ged/c p 01y’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 4.0 m per side, share a 12-cm-thick brick wall. B8,ailzzcmh 06b hjo(5 ecause of a number of 100-W lightbulbs in one room, the air is0hbj( 6zacz,mlo i5h8 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 qvo0cfhtwlxhq(9 yziz5 l8bv(c8cf* / gw8*1 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 ha.sm13tlxodg9;l /tg,3zs o same length and cross-sectional area are attached end to end (Fig. 14–18). The copper end is placed i. x go 3hts/tzodllg1a ;3s9m,n 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 qy 5wn(i+yq:cat which the whole Earth receives energq(yyniw5+ qc:y from 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 through tz8uyuy6w 1q /a glass bulb that has a radius of 3.0 cm and is 1 1 z8/tuuwq6yy.0 mm thick. What is the difference in temperature between the inner and outer surfaces of the glass?   $^{\circ}C $

  Suppose the insulating qualities of the wall of a house come mainnr 57t7cdmip,b9)wn7w. qj lkly 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 sucnb7kn.7rqt9d wpj ,57lm icw)h 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 byzmhzmg:fc-5 m 6u8 j0m an air space, Fig. 14–20. (m58gmchf-zm: zm0u 6j a) Show that the rate of heat flow through such a window by conduction is given 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 take 11.0 kg of ice at dusv zpwg );-v6)tj0g 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*8emv :x-g9nosxo0 jn 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 thermal energy is 9qlv( rgshswu. p83zsctl45. contained in the world’s oceans, estimate the heat liberated when a cube of ocean water, 1 km on each side, is cooled by 1 K. (Approximate the ocean water a3qpsg54ws stlzr. ch.l u9v(8 s pure water for this estimate.)    $ \times10^{ 15}\,J$

  A 15-g lead bullet is tested by firing it into a fi:/za--)yvk ayh 5ozm lxed block of wood with a mass of 1.05 kg. The block and imbedded bullet toge/vka)yh z:az- 5yl-mo ther 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, assuming gums ucprz-)6( vnq6n/ . i7cnit to be a perfect emittercv7n/6m(. uznc)r niqu-6g ps 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 70-kg peg v.c+8-kz t 0(xog2egkl gt+hrson 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 top of a cliff and falls a vertical hk;*25qy4sfg 3wx8 zz0j g rmsfeight of 140 m before striking the grouxfgss* 20yzgf5z4k3rmw8j q ;nd. 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 initiallyz7e0dgbh gni g13zz;8 at 18zndg3z hz70ggi ;be 20.0$^{\circ} C$. 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 with total suqdl0g qn8 9,dfrface area 0 qlg df8nq9d,$1.2\,m^2$ 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 metabolp0yauuri; 2s +ism 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 conducted from nqz h,d(aym+0gm4*q;x m t:gj the interior of the body to the surface. Assume that the thickness of tissue is 4.0 cm, that ;g*m+ym(atz q : xqnd4hgmj,0the 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 cm thick (assume c(n5q8z*skf.58uom ydptk) he onductivity of air) and aqdsf okpm*h( ) zety8n5u85 k.rea $410\,m^2$ 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 qpzaob;yb 14+8b kpt5$220\,m/s$ 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 par0b9aw*n0ga8np*( 1retne ) el 4 bbkdrt (a) in Problem 58, take into account radiation from the leaf to calculate how much water must be transpired (evaporated) by the leaf per hour to maintaidbr *ne*9tb ra () pg4 enaenwbk8l001n a temperature of 35$^{\circ} C$.    g/h

  An iron meteorite melts when it enter/y h.ta)ng)t*rf.vi9n gql4v s the Earth’s atmosphere. If its initial temperature was.g *a4gnn/q )hry.vitf lv 9t) -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 u- g056 l/ yz v0onqyg dn*x21axn9lwvEarth’s crust 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 xgp4v -4te* j +*fzifut*(lw zsquash (Fig. 14–22), two people hit a soft rubber ball at a wall until they are about to drop g 4*p*v( 4t+utj zzfel-f xwi*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 equal1p vttn0 2kz ioo;bzi b4)y.q6 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 andnhn g:/at 7p*z radiation at a rate of about 200 W. Estimate how long it would take z/:nn* gh 7tpafor 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 and dishwashing, ther .lr3buz+ zu6se is “no hot water” left in the 50-gal (185-L) water heater. This suggests that the tank has emptied and refilled with water su. +3lrz6zubat 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 o ojh).09 :oo0gadvp2wlb xoba 3mx.g 3f 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.    $^{\circ} C$