Bartleby Sitemap - Textbook Solutions
All Textbook Solutions for Conceptual Physics: The High School Physics Program
3AWhat happens to the density of a uniform piece of wood when we cut it in half?5AWhich has the greater density—a heavy bar of pure gold or a pure gold ring?7AWhat is the difference between mass density and weight density?a. What is the evidence for the claim that steel is elastic? b. That putty is inelastic?What is Hookes law?What is an elastic limit?A 2-kg mass stretches a spring 3 cm. How far does the spring stretch when it supports 6 kg? (Assume the spring has not reached its elastic limit.)13AWhere is the neutral layer in a horizontal beam that supports a load?Why is the cross section of a metal beam I-shaped and not rectangular?What is the weight—strength relationship in scaling?a. If the linear dimensions of an object are doubled, how much does the total area increase? b. How much does the volume increase?18AWhich will cool a drink faster—a 10-gram ice cube or 10 grams of crushed ice?20AYou take 1000 milligrams of a vitamin. Your friend takes 1 gram of the same vitamin. Who takes more?Your friend says that the primary difference between a Solid and a liquid is the kind of atoms in the material. Do you agree or disagree, and why?How does the density of a 100-kg iron block compare with the density of an iron filing?Which has more volume—a kilogram of lead or a kilogram of aluminum?Which has more weight—a liter of ice or a liter of water?A certain spring stretches 1 cm for each kilogram it supports. a. If the elastic limit is not reached, how far will it stretch when it supports a load of 8 kg? b. Suppose the spring is placed next to an identical spring so the two side-by-side springs equally share the 8-kg load. How far will each spring stretch?A thick rope is stronger than a thin rope of the same material. Is a long rope stronger than a short rope?28ACompression and tension stress occurs in a beam that supports a load (even when the load is its own weight). Show by means of a simple sketch an example where a horizontal load-carrying beam is in tension at the top and compression at the bottom. Then show a case where the opposite occurs: compression at the top and tension at the bottom.Consider a model steel bridge that is 1/100 the exact scale of the real bridge that is to be built. a. If the model bridge weighs 50 N, what will the real bridge weigh? b. If the model bridge doesnt appear to sag under its own weight, is this evidence that the real bridge, built exactly to scale; will not appear to sag either? Explain.Only with great difficulty can you crush an egg when squeezing it along its long axis, but it breaks easily if you squeeze it side-ways.Archie designs an arch to serve as an outdoor sculpture in a park. The arch is to be a certain width and a certain height. To achieve the size and shape for the strongest arch, Archie suspends a chain from two supports of equal heights that are as far apart as the arch is wide. Archie allows the chain to hang as low as the arch is high. He builds the arch to have exactly the shape of the hanging chain, but inverted. Explain why.Why is cement not needed between the stone blocks of an arch that has the shape of an inverted catenary?34AIf you were trapped on a cold mountain, why would it make sense for you to sit in a crouched position and grab your knees? (Hint: A piece of wire will cool faster when stretched out than when rolled up into a ball.)Animals lose heat through the surface areas of their skin. A small animal, such as a mouse, uses a much larger proportion of its energy to keep warm than does a large animal, such as an elephant. Why is the rate of heat loss per unit area greater in a small animal than a large one?Why is heating more efficient in large apartment buildings than in single-family dwellings?Some environmentally conscious people build their homes in the shape of domes. is less heat lost in a dome-shaped dwelling?39AWhich fall faster, large or small raindrops?A one-cubic-centimeter cube has sides 1 cm in length. What is the length of the sides of a cube of volume two cubic centimeters?42A43AA solid 5.0-kg cylinder is 10 cm tall with a radius of 3.0 cm. Show that its density is 18g/cm3.45AWhat is the weight of a cubic meter of cork? Could you lift it? (For the density of cork, use 400kg/m3.)A certain spring stretches 3 cm when a load of 15 N is suspended from it. How much will the spring stretch if 45 N is suspended from it (and the spring doesnt reach its elastic limit)?If a certain spring stretches 4 cm when a load of 10 N is suspended from it, how much will the spring stretch if it is cut in half and 10 N is suspended from it?Consider eight one-cubic-centimeter sugar cubes stacked two-by-two to form a single bigger cube. What will be the volume of the combined cube? How does its surface area compare to the total surface area of the eight separate cubes?Consider eight little spheres of mercury, each with a diameter of 1 millimeter. When they coalesce to form a single sphere, how big will it be? How does its surface area compare to the total surface area of the previous eight little spheres?Distinguish between pressure and force.What is the relationship between liquid pressure and depth of a liquid? Between liquid pressure and density?a. By how much does the water pressure on a submarine change when the submarine dives to double its previous depth (neglect the very real effect of atmospheric pressure above)? b. If the submarine operated in fresh water, would the pressure it feels be greater or less than at the same depth in salt water?How does water pressure 1 meter below the surface of a small pond compare with water pressure 1 meter below the surface of a huge lake?If you immerse a tin can with a small hole in it in water so that water spurts through the hole, what will be the direction of water flow where the hole is?Why does the buoyant force act upward for an object submerged in water?How does the buoyant force that acts on a fish compare with the weight of the fish?Why does the buoyant force on submerged objects not act sideways?How does the volume of a completely submerged object compare with the volume of water displaced?When an object is said to be immersed in water, does this mean it is completely submerged? Does it mean it is partially submerged? Does the word immersed apply to either case?What is the mass of 1 liter of water in kilograms? What is its weight in newtons?a. Does the buoyant force on a submerged object depend on the weight of the object itself or on the weight of the fluid displaced by the object? b. Does it depend on the weight of the object itself or on its volume? Defend your answer.When the buoyant force on a submerged object is equal to the weight of the object, how do the densities of the object and water compare?When the buoyant force on a submerged object is more than the weight of the object, how do the densities of the object and water compare?When the buoyant force on a submerged object is less than the weight of the object, how do the densities of the object and water compare?16ADoes the buoyant force on a floating object depend on the weight of the object itself or on the weight of the fluid displaced by the object? Or are these both the same for the special case of floating?What is the buoyant force that acts on a 100-ton ship? (To make things simple, give your answer in tons.)According to Pascals principle, what happens to the pressure in all parts of a confined fluid when you produce an increase in pressure in one part?When the pressure in a hydraulic press is increased by an additional 10N/cm2, how much extra load will the output piston support when its cross-sectional area is 50 square centimeters?Calculate the amount of pressure you experience when you balance a 5-kg ball on the tip of your finger, say of area 1cm2.Calculate the water pressure at the base of Hoover Dam. The depth of water behind the dam is 220 m. (Neglect the pressure due to the atmosphere.)Calculate the water pressure in the pipes at the bottom of a high-rise building that is fed by a reservoir 30 m above on the roof.An 8.6-kg piece of metal displaces 1 liter of water when submerged. Calculate its density.A 4.7-kg piece of metal displaces 0.6 liter of water when submerged. Calculate its density.Stand on a bathroom scale and read your weight. When you lift one foot up so you're standing on the other foot, does the reading change? Does a scale read force or pressure?Which is more likely to hurt—being stepped on by a man wearing loafers or being stepped on by a half-as-heavy woman wearing spike heels? Defend your answer.Why are persons who are confined to bed less likely to develop bedsores on their bodies if they use a waterbed rather than an ordinary mattress?The sketch shows a reservoir that supplies water to a farm. It is made of wood and is reinforced with metal hoops. a. Why is it elevated? b. Why are the hoops closer together near the bottom part of the tank?30AIn a deep dive, a whale is appreciably compressed by the pressure of the surrounding water. What happens to the whales density?Which teapot holds more liquid?What physics principle accounts for the observation that water seeks its own level?34AIf liquid pressure were the same at all depths, would there be a buoyant force on an object submerged in the liquid? Explain.If a 1-L container is immersed halfway in water, what volume of water is displaced? What is the buoyant force on the container?How much force is needed to push a nearly weightless but rigid 1-L carton beneath a surface of water?Why will a volleyball held beneath the surface of water have more buoyant force than if it is floating?A barge filled with scrap iron is in a canal lock. If the iron is thrown overboard, does the water level at the side of the lock rise, fall, or remain unchanged? Explain.Would the water level in a canal lock go up or down if a ship in the lock were to sink?A ship sailing from the ocean into a fresh-water harbor sinks slightly deeper into the water. Does the buoyant force on it change? If so, does the force increase or decrease?Suppose you have two life preservers that are identical in size, the first a light one filled with foam and the second a very heavy one filled with lead pellets. If you submerge these life preservers in water, upon which will the buoyant force be greater? Upon which will the buoyant force be ineffective? Why are your answers different?When the block of wood is placed in the beaker, what happens to the scale reading? Answer the same question for an iron blockWhen an ice cube in a glass of water melts, does the water level in the glass rise, fall, or remain unchanged? Does your answer change if the ice cube contains many air bubbles? Does your answer change if the ice cube contains many grains of heavy sand?In the hydraulic arrangement shown, the larger piston has an area that is 50 times that of the smaller piston. The strong man hopes to exert enough force on the large piston to raise the 10 kg that rests on the small piston. Do you think he will be successful? Explain.Hydraulic devices multiply forces. Why does this not violate the law of conservation of energy?Which produces more pressure on the ground, an elephant or a woman balancing on high heels? Assume an elephant weighs 500 times more than the woman, and the cross-sectional area of its feet is 10,000 times greater than that of the womans heels.A hole of area 12cm2 is made in the bottom of a barge 1.5 m below the freshwater surface. A board is held over the hole from inside the barge to stop water from leaking in. Show that the force necessary to hold the board in position is 18 N.49AA dike in Holland springs a leak through a hole of area 1cm2 at a depth of 2 m below the water surface. With what force would a boy have to push on the hole with his thumb to stop the leak? Could he do it?When a 1.8-kg wrench is suspended in water from a spring scale, the scale reading is 1.6 kg. What is the density of the wrench?A 13.5-kg block of metal displaces 5 liters of water when submerged. What kind of metal is likely to compose the block?Phil can support 100 N of iron =78,000kg/m3 in water. How many newtons can he support in air?A 1-kg rock suspended above water weighs 10 N. When the rock is suspended beneath the surface of the water, the scale reads 8 N. a. What is the buoyant force on the rock? b. If a container of water on a bathroom-type scale weighs 10 N, what is the scale reading when the rock is suspended beneath the surface of the water? c. What is the scale reading when the rock is released and rests at the bottom of the container?A merchant in Katmandu sells you a solid gold 1.000-kg statue for a very reasonable price. You wonder whether or not you got a bargain, so you lower the statue into a measuring cup and measure its volume. What volume will verify that its pure gold?A prospector desires to know if a nugget is pure gold. The nugget has a mass of 380 grams on a balance. When immersed in water its mass appears as 350 grams. Is the nugget pure gold?Consider a friend of mass 100 kg who can just barely float in fresh water. Show that the volume of your friend is about 0.1m3.A gravel barge, rectangular in shape, is 4 m wide and 10 m long. When loaded, it sinks 2 m in the water. Show that the weight of gravel in the barge is 800,000 N.A rectangular barge 5 m long and 2 m wide floats in fresh water. a. Show that the barge will sink 5 cm lower when loaded with 500 kg of sand. b. If the barge can only be pushed 10 cm deeper into the water before water overflows to sink it, how many kilograms of sand can it carry?A circus elephant weighing 18,800 N is taken on board a barge of length 6.2 m and breadth 3.0 m, which floats in a river. Show that the barge sinks 10 cm when the elephant gets on board.In the hydraulic pistons shown in the sketch, the small piston has a diameter of 2 cm and the large piston has a diameter of 6 cm. How much force can the larger piston exert compared with the force applied to the smaller piston?Try to float an egg in water. Then dissolve salt in the water until the egg floats. How does the density of an egg compare with the density of tap water? Salt water? How do you know?Punch a couple of holes in the bottom of a water-filled container, and water will spurt out because of water pressure (left of figure). Now drop the container and watch what happens. Explain your observations. (Hint: What happens to g, and hence weight, and hence pressure in the reference frame of the falling container?)Make a Cartesian diver like the one shown below. Completely fill a large, pliable plastic bottle with water. Partially fill a small pill bottle so that it just barely floats when capped, turned upside down, and placed in the large bottle. (You may have to experiment to get it just right.) Once the pill bottle is barely floating, secure the lid or cap on the large bottle so that it is airtight. When you press the sides of the large bottle, the pill bottle sinks; when you release it, the bottle returns to the top. Experiment by squeezing the bottle different ways to get different results. Explain the behavior you see.1AHow does the density of gases at different elevations in the atmosphere differ from the density of liquids at different depths?What causes atmospheric pressure?Why doesnt the pressure of the atmosphere break windows?What is the mass of a cubic meter of air at 20C at sea level?6A7AHow does the pressure at the bottom of the 76-cm column of mercury in a barometer compare with the pressure due to the weight of the atmosphere?When you drink liquid through a straw, it is more accurate to say the liquid is pushed up the straw rather than sucked up the straw. What exactly does the pushing? Explain.Why will a vacuum pump not operate for a well that is deeper than 10.3 m?The atmosphere does not ordinarily crush cans. Yet it will crush a car, after it has been heated, capped, and cooled. Why?What property of atmospheric pressure is used by an aneroid barometer?When air is compressed, what happens to its density?A piston in an airtight pump is withdrawn so that the volume of the air chamber is increased five times. What is the change in pressure?When you squeeze an air-filled toy balloon to half size, how does the air pressure inside change?a. How much buoyant force acts on a 1-N balloon suspended at rest in air? b. What happens if the buoyant force decreases? c. What happens if the buoyant force increases?When the speed of a fluid flowing in a horizontal pipe increases, what happens to the internal pressure in the fluid?18AIn addition to Bernoullis principle, what other physics explains the lift produced by an airplane wing?Why does a spinning ball curve in flight?Calculate the density of a gas with a mass of 4.29 kg and a volume of 3.0 cubic meters. Express your answer in kg/m3.Calculate the density of a gas with a mass of 0.00020 kg and a volume of 1.0 liter. Express your answer in kg/m3. P1V1=P2V2An inflated balloon has internal pressure P1. Use Boyles law to calculate the pressure P2 when the balloon is compressed to half its volume.Use Boyles law to calculate the pressure on the same balloon if it instead expands to twice its volume. P=FACalculate the lift on a model airplane wing with an area on one side of 100cm2 and a difference in air pressure above and below the wing of 0.01N/cm2.We can understand how pressure in water depends on depth by considering a stack of bricks. The pressure below the bottom brick is determined by the weight of the entire stack. Halfway up the stack, the pressure is half as great as it is at the bottom because the weight of the bricks above is half as great. To explain atmospheric pressure, we should consider compressible bricks, like foam rubber. Why is this so?27AWhich would weigh more—a bottle filled with helium gas, or the same bottle evacuated?29AFrom Table 20.1, which filling would be more effective in making a balloon rise—helium or hydrogen? Why?A helium-filled balloon pulls upward on its string. Your friend says the upward force is evidence that atmospheric pressure is greater at the bottom of the balloon than on the top. Another friend says such a small difference in altitude wouldnt make a difference in atmospheric pressure. They both look to you for an answer. What do you tell them?32AHow would the density of air at the bottom of a deep mine shaft compare to the density of the atmosphere at the surface of the ground?Atmospheric pressure is nicely demonstrated with the pair of hemispheres shown below. When placed together, the hemispheres make up a hollow sphere. After a vacuum pump evacuates much of the air inside, a considerable force is needed to separate the hemispheres. Suppose two people find they must pull with 150 N each to separate them. If instead, one end of the sphere is attached to a wall and only one person pulls the other end, how much force would the one person have to supply to separate the hemispheres?Relative to sea level, would it be slightly more difficult or somewhat easier to drink through a straw at the bottom of a deep mine? At the top of a high mountain? Explain.If there were a liquid twice as dense as mercury, and if it were used to make a barometer, how tall would the column be?Before boarding an airplane, you buy a bag of chips (or any item sealed in an airtight foil package) and, while in flight, you notice that the bag is puffed up. Explain why this occurs.Why do you suppose that airplane windows are smaller than bus windows?Why do your ears pop' when you ascend to higher altitudes?40AWhen you squeeze an air-filled toy balloon, its volume decreases. Your friend says that the mass and the density of air inside increase. Do you agree with your friend? Defend your response.42AIt is easy to breathe when snorkeling with only your face beneath the surface of the water, but quite difficult to breathe when you are submerged nearly a meter, and nearly impossible when you are more than a meter deep (even if your snorkel tube reaches to the surface). Figure out why, and explain carefully.44Aa. Would a balloon rise in an atmosphere where the pressure was somehow the same at all altitudes? b. Would a balloon rise in the complete absence of atmospheric pressure (for example, at the surface of the moon)?The buoyant force of air is considerably greater on an elephant than on a small helium-filled balloon. Why, then, does the elephant remain on the ground, while the balloon rises?Why is it that when cars pass each other at high speeds on the road, they tend to be drawn to each other?In a department store, an air stream from a hose connected to the exhaust of a vacuum cleaner blows upward at an angle and supports a beach ball in midair. Which is more effective in keeping the ball up—air blowing across the top or air blowing across the bottom of the ball?What physics principle underlies the following three observations? When passing an oncoming truck on the highway, your car tends to swerve toward the truck. The canvas roof of a convertible automobile bulges upward when the car is traveling at high speeds. The windows of older passenger trains sometimes break when a high-speed train passes by on the next track.50AThe diameter of a fire hose varies with the flow rate of water inside. The hose may be relatively narrow, and at another time puffed up like a fat snake. In which case is water flowing fast, and when is water hardly flowing at all?You overhear a conversation between two physics types. One says that birds couldnt fly before the time of Bernoulli. The other says that it was not so. Birds could fly before the time of Bernoulli but couldnt fly before the time of Newton. Humor aside, what points are they making?Explain how an airplane is able to fly upside down.A typical school gym is about 60.0m30.0m10.0m. Show that the mass of air in the gym on a 20C day is around 22,000 kg.The 'height' of the atmosphere is about 30 km. The radius of Earth is 6400 km. What percentage of Earths radius is the height of the atmosphere?56AAverage atmospheric pressure at Earths surface is 1.01105N/m2. Earths radius is 6.37106m. Show that the total weight of Earths atmosphere is about 5.151019N.A party balloon is squeezed to 2/3 of its initial volume. Show that the pressure in the balloon is increased by 1.5 times.An automobile is supported by four tires inflated to a gauge pressure of 180 kPa. The area of contact of each of the tires (ignoring the effects of tread thickness) is 190cm2 (which means the total area of tire contact is 0.076m2 ). Estimate the mass of the car in kilograms.60AA mercury barometer reads 760 mm at sea level. When it is carried to an altitude of 5.6 km, the height of the mercury column is reduced to half its initial value, or 380 mm. a. What is the air pressure at this altitude relative to sea-level pressure? b. If the barometer is taken up another 5.6 km to an altitude of 11.2 km, will the height of its mercury column fall another 380 mm and be zero? Why or why not?62AReferring to the previous problem, find the volume of the displaced air.In 1982 Larry Walters ascended from his home in Long Beach, California, to an altitude of 4900 m (16,000 ft) after tying 42 helium-filled, 1.9-m diameter weather balloons to his patio chair. Show that the buoyant force on these balloons at sea level would be 1800 N.How many newtons of lift are exerted on the wings of an airplane that have a total area of 100m2 when the difference in air pressure below and above the wings is 5% of atmospheric pressure?Try this in the bathtub or while washing dishes. Lower a glass, mouth downward, over a small floating object as shown. What happens? How deep would the glass have to be pushed to compress the enclosed air to, half its volume? (Hint: You cant do this in your bathtub unless its 10.3 m deep!)Place a card over the open top of a glass filled to the brim with water, and invert it. What happens? Why? Try turning the glass sideways as shown below.Fill a bottle with water and hold it partially under water so that its mouth is beneath the surface. What happens to the water in the bottle? Explain. How tall would the bottle have to be before water ran out? (Hint: You cant do this indoors unless you have a ceiling 10.3 m high!)Hold a spoon in a stream of water, as shown. Describe and explain the effect in terms of the differences in pressure.1A2A3A4A5AWhat is meant by saying that a thermometer measures its own temperature?7AWhat is internal energy?What is the difference between a calorie and a Calorie?What is the difference between a calorie and a joule?What does it mean to say that a material has a high or low specific heat capacity?Do substances that heat up quickly normally have high or low specific heat capacities?How does the specific heat capacity of water compare with that of other common substances?14AWhy does a bimetallic strip curve when it is heated (or cooled)?Which expands most for increases in temperature: solids, liquids, or gases?17AIce is less dense than water because of its open crystalline structure. But why is water at 0C less dense than water at 4C?Why do lakes and ponds freeze from the top down rather than from the bottom up?Why do shallow lakes freeze quickly in winter, and deep lakes not at all?The four plastic-foam soup bowls contain the same amount of water at 20C. You also have a batch of 100-g copper cylinders that have initial temperatures as shown. The cylinders are submerged in the bowls. Rank the bowls according to the maximum temperature of the water after the cylinders are added.Four plastic-foam soup bowls contain the same amount of water at 20C. You dunk cylinders of different metals, but of equal masses, in the bowls. All four cylinders have been in a hot oven and have the same temperature. (See Table 21.1 for specific heat capacities of these metals.) Rank the bowls according to the maximum temperature of the water after the cylinders are added.23ACalculate the number of calories given off by 500 grams of water cooling from 50C to 20C.A 30-gram piece of iron is heated to 100C and then dropped into cool water where the irons temperature drops to 30C. How many calories does it lose to the water? (The specific heat capacity of iron is 0.11cal/gC.)Suppose a 30-gram piece of iron is dropped into a container of water and gives off 165 calories in cooling. Calculate the irons temperature change.What mass of water will give up 240 calories when its temperature drops from 80C to 68C?When a 50-gram piece of aluminum at 100C is placed in water, it loses 735 calories of heat while cooling to 30C. Calculate the specific heat capacity of the aluminum.29AWhich is greater, an increase in temperature of 1C or an increase of 1F?31AThe temperature of the suns interior is about 107 degrees. Does it matter whether this is degrees Celsius or kelvins? Defend your answer.33AIf you take a bite of hot pizza, the sauce may burn your mouth while the crust, at the same temperature, will not. Explain.In the old days, on a cold winter night it was common to bring a hot object to bed with you. Which would be better—a 10-kilogram iron brick or a 10-kilogram jug of hot water at the same temperature? Explain.In addition to the overall motion of molecules that is associated with temperatures some molecules can absorb large amounts of energy in the form of internal vibrations and rotations of the molecules themselves. Would you expect materials composed of such molecules to have a high or a low specific heat capacity? Why?37A38A39AOn a hot day, you remove from a picnic cooler a chilled watermelon and some chilled sandwiches. Which will remain cool for a longer time? Why?Why is it important to protect water pipes so they dont freeze?Iceland, so named to discourage conquest by expanding empires, is not at all ice-covered like Greenland and parts of Siberia, even though it is nearly on the Arctic Circle. The average winter temperature of Iceland is considerably higher than regions at the same latitude in eastern Greenland and central Siberia. Why is this so?A metal ball is just able to pass through a metal ring. When the ball is heated, thermal expansion will not allow it to pass through the ring. What would happen if the ring, rather than the ball, were heated? Would the ball pass through the heated ring? Does the size of the hole in the ring increase, decrease, or stay the same?After a machinist slips a hot, snugly fitting iron ring over a cold brass cylinder, the ring becomes 'locked' in position and cant be removed even by subsequent heating. This procedure is called shrink fitting.' How does it occur? Can you conclude anything about the thermal expansion rates of iron and brass?45AWould a bimetallic strip function if the two different metals happened to have the same rates of expansion? Is it important that they expand at different rates? Explain.Cite an exception to the claim that all substances expand when heated.An old remedy for a pair of nested drinking glasses that stick together is to run water at different temperatures into the inner glass and over the surface of the outer glass. Which water should be hot, and which cold?State whether water at the following temperatures will expand or contract when warmed: 0C;4C;6C.Suppose that water is used in a thermometer instead of mercury. If the temperature is at 4C and then changes, why cant the thermometer indicate whether the temperature is rising or falling?If water had a lower specific heat capacity, would lakes be more likely or less likely to freeze in the winter?How does the combined volume of the billions and billions of hexagonal open spaces in the crystals in a piece of ice compare with the portion of ice that floats above the surface of the water?People in the pioneering days placed hot potatoes in their pockets on cold winter days to keep their hands warm. Assuming that a potato is mostly water, Andrew calculates 24,000 calories of heat are released by a 350-g potato that cools from 85C to 15C. Alexis calculates that 102,000 joules of heat are released. Whose answer do you agree with, and why?If you wished to warm 100 kg of water by 15C for your bath, how much heat would be required? (Give your answer in calories and joules.)Anthonys thin plastic water bottle holds 500 mL of water at temperature 28C. He puts it into the refrigerator. Show that the refrigerator removes 50,000 J of heat from the water to cool it to 4C.56AWhat would be the final temperature of the mixture of 50 g of 20C water and 50 g of 40C water?What would be the final temperature if you mixed a liter of 20C water with 2 liters of 40C water?What would be the final temperature if you mixed a liter of 40C water with 2 liters of 20C water?What would be the final temperature when 100 g of 25C water is mixed with 75 g of 40C water?What will be the final temperature of 100 g of 20C water when 100 g of 40C iron nails are submerged in it? (The specific heat of iron is 0.12cal/gC.)What is the specific heat capacity of a 50-gram piece of 100C metal that will change 400 grams of 20C water to 22C?Taylor finds that a certain amount of heat raises the temperature of a Sample of iron by 10C. Show that the same amount of heat will raise the temperature of an equal mass of lead by 35C.Suppose that a metal bar 1 m long expands 0.5 cm when it is heated. How much would it expand if it were 100 m long?Steel expands 1 part in 100,000 for each Celsius degree increase in temperature. If the 1.5-km main span of a steel suspension bridge had no expansion joints, how much longer would it be for a temperature increase of 20C?A cook pours L of ice water at 0C into a pan of hot water at 80C and finds that the mixture reaches a temperature of 60C. How much hot water was in the pan?Your (perfectly insulated) bathtub has 82 liters of water in it, but it has cooled down to a temperature of 39C. You'd like to add just the right amount of 50C water to the tub to make your bathwater the perfect temperature of 42C. Show that adding 31 liters of 50C water to the tub will accomplish this goal.What is the role of 'loose' electrons in heat conductors?Why does a piece of room-temperature metal feel cooler to the touch than paper, wood, or cloth?What is the difference between a conductor and an insulator?Why are materials such as wood, fur, feathers, and even snow good insulators?5AHow does Archimedes' principle relate to convection?Why does the direction of coastal winds change from day to night?How does the temperature of a gas change when it is compressed? When it expands?9AWhat is radiant energy?How does the predominant frequency of radiant energy vary with the absolute temperature of the radiating source?Is a good absorber of radiation a good emitter or a poor emitter?Which will normally cool faster, a black pot of hot tea or a silvered pot of hot tea?Why does a good absorber of radiant energy appear black?15AWhich will undergo the greater rate of cooling, a red-hot poker in a warm oven or a red-hot poker in a cold room (or do both cool at the same rate)?Does Newtons law of cooling apply to warming as well as to cooling?What is terrestrial radiation?Solar radiant energy is composed of short waves, yet terrestrial radiation is composed of relatively longer waves.20AAt what common temperature will both a block of wood and a piece of metal feel neither hot nor cool when you touch them with your hand?If you stick a metal rod in a snowbank, the end in your hand will soon become cold. Does cold flow from the snow to your hand?Wood is a better insulator than glass. Yet fiberglass is commonly used as an insulator in wooden buildings. Explain.Visit a snow-covered cemetery and note that the snow does not slope upward against the gravestones but, instead, forms depressions around them, as shown. Make a hypothesis explaining why this is so.Wood is a poor conductor, which means that heat is slow to transfer—even when wood is very hot. Why can firewalkers safely walk barefoot on red-hot wooden coals, but not safely walk barefoot on red-hot pieces of iron?When a space shuttle is in orbit and there appears to be no gravity in the cabin, why can a candle not stay lit?A friend says that, in a mixture of gases in thermal equilibrium, the molecules have the same average kinetic energy. Do you agree or disagree? Defend your answer.A friend says that, in a mixture of gases in thermal equilibrium, the molecules have the same average speed. Do you agree or disagree? Defend your answer.In a mixture of hydrogen and oxygen gases at the same temperature, which molecules move faster? Why?Which atoms have the greater average speed in a mixture, U-238 or U-235? How would this affect diffusion through a porous membrane of otherwise identical gases made from these isotopes?Notice that a desk lamp often has small holes near the top of the metal lampshade. How do these holes keep the lamp cool?Turn an incandescent lamp on and off quickly while you are standing near it. You feel its heat, but you find when you touch the bulb that it is not hot. Explain why you felt heat from the lamp.In Montana, the state highway department spreads coal dust on top of snow. When the sun comes out, the snow rapidly melts. Why?Suppose that a person at a restaurant is served coffee before he or she is ready to drink it. In order that the coffee be hottest when the person is ready for it, should cream be added to it right away or just before it is drunk?Will a can of beverage cool just as fast in the regular part of the refrigerator as it will in the freezer compartment? (What physical law do you think about in answering this?)36AIf you wish to save fuel on a cold day, and you're going to leave your warm house for a half hour or so, should you turn your thermostat down a few degrees, down all the way, or leave it at room temperature?Why is whitewash sometimes applied to the glass of florists' greenhouses? Would you expect this practice to be more prevalent in winter or summer months?If the composition of the upper atmosphere were changed so that it permitted a greater amount of terrestrial radiation to escape, what effect would this have on Earths climate? Conversely, what would be the effect if the upper atmosphere reduced the escape of terrestrial radiation?An automobile cooling system holds 12 liters of water. Show that when its temperature rises from 20C to 70C, it absorbs 60 kilocalories.41ADecay of radioactive isotopes of thorium and uranium in granite and other rocks in Earths interior provides sufficient energy to keep the interior molten, heat lava, and provide warmth to natural hot springs. This is due to the average release of about 0.03 J per kilogram each year. Show that 13.3 million years are required for a chunk of thermally insulated granite to increase 500C in temperature. (Use 800J/kgC for the specific heat capacity of granite.)In a lab you burn a 0.6-g peanut beneath 50 g of water. Heat from the peanut Increases the water temperature from 22C to 50C. a. Assuming 40% efficiency, show that the food value of the peanut is 3500 calories (3.5 Calories). b. What is the food value in Calories per gram?Pounding a nail into wood makes the nail warmer. Suppose a hammer exerts an average force of 500 N on a 6-cm nail whose mass is 5 grams when it drives into a piece of wood. Work is done on the nail and it becomes hotter. If all the heat goes to the nail, show that its increase in temperature is slightly more than 13C. (Use 450J/kgC for the specific heat capacity of the nail.)At a certain location, the solar power per unit area reaching Earths surface is 200W/m2, averaged over a 24-hour day. Consider a house with an average power requirement of 3 kW with solar panels on the roof that convert solar power to electric power with 25 percent efficiency. Show that a solar collector area of 60 square meters will meet the 3 kW requirement.Hold the bottom end of a test tube full of cold water in your hand. Heat the top part in a flame until the water boils. The fact that you can still hold the bottom shows that water is a poor conductor of heat. This is even more dramatic when you wedge chunks of ice at the bottom; then the, water above can be brought to a boil without melting the ice. Try it and see.If you live where there is snow, do as Benjamin Franklin did more than two centuries ago and lay samples of light and dark cloth on the snow. (If you dont live in a snowy area, try this using ice cubes.) Describe differences in the rate of melting beneath the cloths.Wrap a piece of paper around a thick metal bar and place it in a flame. Note that the paper will not catch fire. Can you figure out why? (Hint: Paper generally will not ignite until its temperature reaches about 230C.)1A2AWhy does a hot dog pant?What is condensation, and why is it also a warming process?