What happens to the work done whsu4r6 g2dq 0qa/xm 1cnf7v 6yoen a jar of orange juice is vigorously shaken?

When a hot object warms a cooler object tx,h yh5(a9ry, does temperature flow between them? Are the temperature changes of the two objects (t h9x5y yh,arequal?

(a) If two objects of different temperaturesol+:zih r, mxr(o kc*(t.w bp( 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 energies of the tr: *wt ck( i(hxb (+l,.orpzmowo objects are the same? Explain.

In warm regions where tropical plants grow but the 5q 3ou,xv7d tknucq -;temperature may drop below freezing a few times in the winter, the destruction of sennqq5 ;,vt3xo7uku-c dsitive plants due to freezing can be reduced by watering them in the evening. Explain.

The specific heat of water is quite large. Ehuni(h5grqpxf- 3:q6b + f /cxxplain why this fact makes water particularly good for he35x/qhh+ri6unp fq -xc(bfg: ating systems (that is, hot-water radiators).

Why does water in a metal canteen stay cooler if the cloth jacket surro./y nb,l)sql5qrl +fbunding the ca,qnf5llb .qb r)+ys /lnteen is kept moist?

Explain why burns caused by steam on the skin are often more severe thas uf7 pxr219men burns ce7s1x2r pufm 9aused by water at 100 $^{\circ} C$ .

Explain why water cools (its tempe6k+w x1x4hx.pvkemlpd) k23 jrature drops) when it evaporates, using the concepts of latent heat .pv6hl+kwemxkx3)2 41d j x kpand internal energy.

Will potatoes cook faster if the water iuu:pmkqugf 594o ;+yp s boiling faster?

Does an ordinary electric fan cooj*(r umym4 wrzh-0er(5p w1tdl the air? Why or why not? If not, why use it?

Very high in the Earth’s atmosphere, the temperature ca +:sfb* u3zbyen be 700 $^{\circ} C$ . Yet an animal there would freeze to death rather than roast. Explain.

Explorers on failed Arctic 1 qv 4os;zbt+iexpeditions have survived by covering themselves with snow. Whyi+z;o4vb t s1q would they do that?

Why is wet sand at the beach cooler to walkb3nvfl x0bu (; on than dry sand?

If you hear that an object has “high heat content,” does that +ro.fc 4et )s0n obt+nmean that its temperature is high? E4rs)c on t0bft.n ++eoxplain.

When hot-air furnaces are used to heat a house, why is it imoikicq) -(rtv p se,251yzcb;+wah.jportant that there be a vent for air to return to the furnace? What hp-jetrcwb,)yci1 k ioh5(a;2sv +.z qappens if this vent is blocked by a bookcase?

Ceiling fans are someth09 ije*dpx 7 i/nhpl*3 xep)vimes reversible, so that they drive the air down in one season and pull it up in another season. Wh 9i*3xj* v xeh)pne 0dhilpp/7ich way should you set the fan for summer? For winter?

Down sleeping bags and parkas are often specified as so many ijymcq1x3 - t9rnches or centimeters of loft, the actual thickness of the garq9 y13-rxmtjcment when it is fluffed up. Explain.

Microprocessor chips hs(4d6.g pwkzl;xaj y+ ave a “heat sink” glued on top that looks like a series of fins. Whya.pjlgs6( xkw4+yd z ; is it shaped like that?

Sea breezes are often encountered on sunny days at the shore idz wp1 ir(7qb: s:r8/jmc8xzof a large body of water. Explain87:izj 1r8qb:wp cdx/(rimz s in light of the fact that the temperature of the land rises more rapidly than that of the nearby water.

The floor of a house/3e3 (ypck)lotgv*7 o0dfisk on a foundation under which the air can flow is often cooler than a floor that rests directly c*ok) ls/eitgf(7kd op33v0y 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 readings are alse+4 5yw9ii4ha7 ab nlrl3,rmways taken with the thermometer in the sha , 94lrbls5rn7 +i3mweaa 4hiyde.

A premature baby in an incu15g*t i8: dc pw7fdxvhbator can be dangerously cooled even when the air temperature in the incubator is warm. f7dt pvcw18 :d*i5 xhgExplain.

Why is the liner of a thermos bottle silvered (Fig. 14–15), and wdn s)hf( 9 cp.22cmvxkoesv/, hy does it have a vacuum becco f(.d29msvk) npx/h2s ev,tween its two walls?

Imagine you have a wall that is 48 dhvots ;9i 5cmcid9w6xo7l very well insulated — it has a very high thermal resist d46d99 ;vt ihw7occoi8 l5mxsance, $R_1$ 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 windoka)4 qh+sfj6o ws 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) For the first three, what is (are) the mechanism(s): conduction, convection, or radiation? (b) Heavy curtain 6af4kho+sqj) s reduce which of these heat losses? Explain in detail.

A piece of wood lying in the Sun absorbs more heat tha lrox . +9jimw:,dv8fen a piece of shiny metal. wm8er ,jid .vx +:olf9Yet the wood feels less hot than the metal when you pick it up. Explain.

The Earth cools off aq1 + / sg/ocqrgcs(0fjt night much more quickly when the weather is clear than when cloudy. +g1(sgo cq0 cfrqs//jWhy?

An “emergency blanket” is a thin shiny (metal coated) plastic ffc+ 7t+x49mdp 8ai uqcoil. Explain how it can help to keep an immobile persoc4c9pi7 +u ft+a8qmxd n warm.

Explain why cities situated by the ocean tend to ha5zov u8llc: 72js5r ieve less extreme temperatures than ls7eri2lz c5jv5 8u:oinland cities at the same latitude.

  How much heat (in joules) is rb5h exv8k)phir vmx:af()ode: m:6c3 equired to raise the temperature of 30.0 kg of water from 15 eh:xx5hv6m)8rd mc ae )io::pv(k3bf$^{\circ} C$ to 95 $^{\circ} C$ ?    $ \times10^{7 }\,J$

  To what temperature will9r wei, n 6wel6lm4w5e 7700 J of heat raise 3.0 kg of water that is initially at 10.0 wler6me6 ,iwew4 l59n$^{\circ} C$ ?    $^{\circ} C$

  An average active person consumes about 250vay,c)) ;o bvu0 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 hm ;qx0l;xzselw5/ 2o British system of units. One Btu is defz5 2 lx e;0m;hlqs/oxwined as the heat needed to raise 1 lb of water by 1 F $^{\circ} $ . Show that
1Btu = 0.252kcal=1055J

  A water heater can generate s+t,2 uz:+smm g5n9h 0p9gyh i6i qlsp$32,000\,kJ/h$ 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. Estimate how long it wiyq/g ln,vw5 r+ll take to heat a cup of soup (assurny/v +gql,5wme this is 250 mL of water) from 20$^{\circ} C$ to 60$^{\circ} C$ .    min

  How many kilocalories aiu+b-n 5b9offug (qo/l8fd c7re generated when the brakes are used to bring a 1200-kg car to rest from a speed ofnglod8u/9i 5f(7c b f+o uq-bf $95\,km/h$ ?    kcal

  An automobile cooling system holds 16 L of water. Hor;ps3w6 6f r6pn v6jxzw much heat does it absorb if itspr v6xp3j6sr zn; f6w6 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 ishb98 aq7q.78x yel efo needed to raif88lxq7. aeq ye hb9o7se 5.1 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 7 )5)xghocuv/rsx6 cwexperience the same temperature rise when they absorb the same amount of heat. What is the ratio of their6w7gvs5c ox)) u/xr hc masses? [Hint: See Table 14–1.]$m_{Cu}$ : $m_{Al}$ : $m_{H_2O}$ =    :    :   

  A 35-g glass thermometer reads 21.6, ip w59jbedn1, ea(px$^{\circ} C$ 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 tev/+ j+xovr 3jxmperature 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 gj1i( cp: bkt-= $0.4\,kg$) 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 heated tc ep4bt7 ;o3uao 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 /m5vlei nx a0:6zlsb6ivc+a2coffeepot to bring to a boil 0.75 L of water initiall a a6v+0/lensibzi m v2:c65xly at 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 ofd;y3o(1l cig5zu:3h lmw) dbi 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 0.725 kg and is placed in 2.00 kg of water contained in an aluminum calorimeter cup of m)u:bw;5 dm3l3 zlcdoih g( y1iass 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(:5rg mhc8zb v 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 iaz 91agn).afy;9dj ma 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 object is defined as the amount of heat needed totgtfd)4,crzy*vn )yw *4a zc 1 raise its tempegtzt*yw,)fad41 c*c)nz y 4 rvrature 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 d6 ojyv.lel l(-yvepk./*ao) initially at 20$^{\circ} C$?    $ \times10^{6 }\,J$

  A 0.095-kg aluminiumxhz *7f lc zdgppajs3 76e:z6b;. liq9 sphere is dropped from the roof of a 45-m-high building. If 65:*hb7j79ac3dpxqelil6spf zg;6 z . z% of the 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)l+;j +kasne-/nu fe s of heat in 30 min by evaporation of wa+akslsnee/ j nuf;-)+ter from 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 melting point is dropped into an insulayg kad5euw x0pk 5bs.a2(,- ltted container of liquid nitrogen. How muchus pad52 k bakg (-0lewx5,.yt nitrogen 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 takeotj,tuq5u4 a+f3gf y (n 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 contains 830 kg of water av4p6m be 6(jo-f:t lwbt 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 bicyclist consumes 8.0 L of whz+/ h)5 +zfnvvqhf8ma2 0wy-zz:bs y ater over the span of four hours. Making thvhns 2fv +y/z h:f0-qh)5+8wmz ba zyze 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 to heat, so our approximation is not far off.)    kcal

  What mass of steam azk8cp )myh+6t j+um(vt 100$^{\circ} C$ 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 mercb0 c/l 80.hl m/bawppqury 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 travelin +c1oagfky,- h27o jwivk/ki:i l*p0mg 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 a ui-wv 1x l,lsdm(9,tmt $6.4\,m/s$ 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 note1 qtcrgbnb.w5+thr5, p8ir8xs that the 8.2-g lead bullet that was stopped in a doorframe 1n+p,xrrrw. b885b ihtc 5gtq 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 di*y/9 u ko l(a:ogml9 b0t6oegiameter 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 bwuo:et(5v9o j y conduction in Example 14–10, assuming that there are strong gusty winds and the external tempereo5 jvtu o9w(:ature is -5$^{\circ} C$   $ \times10^{4 }$ W

  (a) How much power is r av1-v-tu. b2p1t obpdadiated 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 3x fffdc+mg2+fc3- gdom6i/iof heat flows by conduction from the blood capillaries beneath the f+ m cf+f3mc6 fx-2/odd g3iigskin 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 4.0 m per side, share a 12-cm-thick brick wall. Becan-t+ 0vf9y5 om svfzx.dl0m k:use of a nu+k s z5nm-x0t.vdv9f:of yl0m mber of 100-W lightbulbs 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 S2slv xqxpx3 xb;6 (1mkun to melt a 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 same length and cros:. hl,le4 tlaps-sectional area are alh p4el:ta.l ,ttached end to end (Fig. 14–18). 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, estimatgbqjcws9 30p+af1cnqt goyi r 26o1(m74t9oge the rate at which the whole Earth receive7019gp 6 yg9 qoncosbc3(qaf+1wt m2 o4grtijs energy 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 dissis :xjq8a6 .43bkvg(ruinzvh/pated through a glass bulb that has a radius of 3.0 cm and is 1.0 mm thick. What is the difference in temperature nx./vgkiazs( :4b8rv hq3j 6u between the inner and outer surfaces of the glass?   $^{\circ}C $

  Suppose the insulating qualities of the wall of a9,r :jqmord3 w 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 r9rwd :oqj3,mis the total 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 st. b kk1dw5jd(ovyahziq . 0k3(-za1ueparated by an air space, Fig. 14–20. (a) Show that the rate of heat flow through suv. a 3(ozk-ddhj(k q15u zbtw.iyk0a1ch 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::1t49+,w/6 lnodti ol qaamc n x(wze 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 consejf1/r l9: 6amoocc .o-g1m jtains 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 hovks 4y/imm8v; w much thermal energy is 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 wakv 4im8s/yvm;ter as pure water for this estimate.)    $ \times10^{ 15}\,J$

  A 15-g lead bullet is tested by firing it into au(z1v;kvvzvxzia +uv6l,u 2 0 fixed block of wood with a mass of 1.05 kg. The block and imbedded bullet together absorb all the heat generated. After thermal equilibrium +z vuu vxvv16zkv0liu;z( a ,2has 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, assumiw-b-(rd 66zpjobzrk )ng it to be a perfect emittep-b (jrz 6wok-)6b rzdr 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 person ma1 f q28:g;xvfmhu/qky7rpk gfa)u2v8 y 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/ m 9lxnktz4x9 and falls a vertical height of 140 m before striking the ground. Estimate the temperature rise of the rock if 50% of the 9 / kl9mxz4txnheat generated remains in the rock.    $C^{\circ} $

  A 2.3-kg lead ball is dropped into a x,th)uy bp; m.2.5-L insulated pail of water initially at 2h;p m)u ,ytx.b0.0$^{\circ} C$. 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 jacke z/hj2p *vn9yv(hi1ynt 3.5 cm thick with total surface area n2 hyhj*(19 yinzp/vv$1.2\,m^2$ 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 averngd l j3y2r6 yf-j6k5apc8yn(age 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 conducted from the interior of the 8a)l2tt-m y,6 wfheh6 nwvs8fbody to the surface. Assume that the thickness of tissul6,vf8etwfwh6myt- n)8sa 2 h e is 4.0 cm, that 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 cm thick (assv9(u,6lpba rp xqw l71ume conductivity of air) and areapa l l7,pxr9vu61b qw( $410\,m^2$ 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 .i 9903boerlunnpu0 oat $220\,m/s$ 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 Problem12jt ei p;ycu6rtzm du 4d73x,-mh8eg 58, take into account radiation from the leaf to calculate how much water must be transpired (evaporate 1ut3 i demp2hdyg; 6cz texr8,-u4jm7d) by the leaf per hour to maintain a temperature of 35$^{\circ} C$.    g/h

  An iron meteorite melts when itjhm34 fb3f2x8cijvd(/au e) f1uod j4 enters the Earth’s atmosphere. If its initial temperature d(u 1m v8f 3cj3jifx)/ohe4fabju d 24was -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 l27fh-r*ugq+zh hz2 vincreases 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 ai m/.i iyxt0 i;n3jrt, soft rubber ball at a wall until they are about to drop due to dehydration and exhaustion. Assume that 0ti it; i y3x,rm./injthe 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 of iwx g d;.3wvfq)ce 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 radiation atxzg88: q:r d5niv*px q a rate of about 200 W. Estimate how long it would take for the body tempevp8dx8z ir:n* q:gq5xrature 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 a qvj/xxp7,o/ +zxar1b nd dishwashing, there is “no hot water” left in the 50-gal (185-L)x pva j/+zxq,xb7o/1 r water 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 glassewbks 28.* p + *haesvx.ma*fw surface 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.    $^{\circ} C$