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physics
college physics a strategic approach 2nd

College Physics A Strategic Approach 2nd Edition Randall D. Knight, Brian Jones, Stuart Field - Solutions

You may have noticed that latex helium balloons tend to shrink rather quickly; a balloon filled with air lasts a lot longer. Bal- loons shrink because gas diffuses out of them. The rate of diffusion is faster for smaller particles and for particles of higher speed. Diffusion is also faster when
How many cubic millimeters (mm3) are in 1 L?
If you buy a sealed bag of potato chips in Miami and drive with it to Denver, where the atmospheric pressure is lower, you will find that the bag gets very "puffy." Explain why.
A box is 200 cm wide, 40 cm deep, and 3.0 cm high. What is its volume in m?
If you double the typical speed of the molecules in a gas, by what factor does the pressure change? Give a simple explanation why the pressure changes by this factor.
Dry ice is frozen carbon dioxide. If you have 1.0 kg of dry ice, what volume will it occupy if you heat it enough to turn it into a gas at a temperature of 20°C?
Two gases have the same number of molecules per cubic meter (N/V) and the same rms speed. The molecules of gas 2 are more massive than the molecules of gas 1. a. Do the two gases have the same pressure? If not, which is larger?b. Do the two gases have the same temperature? If not, which is larger?
What is the absolute pressure of the air in your car's tires, in psi, when your pressure gauge indicates they are inflated to 35.0 psi? Assume you are at sea level.
a. Which contains more particles, a mole of helium gas or a mole of oxygen gas? Explain. b. Which contains more particles, a gram of helium gas or a gram of oxygen gas? Explain.
You have 100 g of aluminum and 100 g of lead. a. Which contains a larger number of moles? Explain. b. Which contains more atoms? Explain.
Many cultures around the world still use a simple weapon called a blowgun, a tube with a dart that fits tightly inside. A sharp breath into the end of the tube launches the dart. When exhaling forcefully, a healthy person can supply air at a gauge pressure of 6.0 kPa. What force does this pressure
When you stifle a sneeze, you can damage delicate tissues because the pressure of the air that is not allowed to escape may rise by up to 45 kPa. If this extra pressure acts on the inside of your 8.4-mm-diameter eardrum, what is the outward force?
A gas cylinder contains 1.0 mol of helium at a temperature of 20°C. A second identical cylinder contains 1.0 mol of neon at 20°C. The helium atoms are moving with a higher average speed, but the gas pressure in the two containers is the same. Explain how this is possible.
7.5 mol of helium are in a 15 L cylinder. The pressure gauge on the cylinder reads 65 psi. What are (a) The temperature of the gas in °C (b) The average kinetic energy of a helium atom?
Mars has an atmosphere composed almost entirely of carbon dioxide, with an average temperature of -63°C. What is the rms speed of a molecule in Mars's atmosphere?
What is the maximum amount of work that a gas can do during a constant-volume process?
You need to precisely measure the dimensions of a large wood. panel for a construction project. Your metal tape measure was left outside for hours in the sun on a hot summer day, and now the tape is so hot it's painful to pick up. How will your measurements differ from those taken by your coworker,
Your car's radiator is made of steel and is filled with water. You fill the radiator to the very top with cold water, then drive off without remembering to replace the cap. As the water and the steel radiator heat up, will the level of water drop or will it rise and overflow? Explain.
A cylinder contains 3.0 L of oxygen at 300 K and 2.4 atm. The gas is heated, causing a piston in the cylinder to move outward. The heating causes the temperature to rise to 600 K and the volume of the cylinder to increase to 9.0 L. What is the final gas pressure?
Materials A and B have equal densities, but A has a larger specific heat than B. You have 100 g cubes of each material. Cube A, initially at 0°C, is placed in good thermal contact with cube B, initially at 200°C. The cubes are inside a well-insulated container where they don't interact with their
A student is heating chocolate in a pan on the stove. He uses a cooking thermometer to measure the temperature of the chocolate and sees it varies as shown in Figure Q12.20. Describe what is happening to the chocolate in each of the three portions of the graph. FIGURE Q12.20 The temp... then
A sample of ideal gas is in a cylinder with a movable piston. 600 J of heat is added to the gas in an isothermal process. As the gas expands, pushing against the piston, how much work does it do?
If you bake a cake at high elevation, where atmospheric pressure is lower than at sea level, you will need to adjust the recipe. You will need to cook the cake for a longer time, and you will need to add less baking powder. (Baking powder is a leavening agent. As it heats, it releases gas bubbles
The specific heat of aluminum is higher than that of iron. 1 kg blocks of iron and aluminum are heated to 100°C, and each is then dropped into its own 1 L beaker of 20°C water. Which beaker will end up with the warmer water? Explain.
If you have two spoons of the same size, one silver and one stainless steel, there is a quick test to tell which is which. Hold the end of a spoon in each hand, then lower them both into a cup of very hot water. One spoon will feel hot first. Is that the silver spoon or the stainless steel spoon?
It is possible to make a thermometer by scaling gas in a rigid container and measuring the absolute pressure. Such a constant- volume gas thermometer is placed in an ice-water bath at 0.00°C. After reaching thermal equilibrium, the gas pressure is recorded as 55.9 kPa. The thermometer is then
If you live somewhere with cold, clear nights, you may have noticed some mornings when there was frost on open patches of ground but not under trees. This is because the ground under trees does not get as cold as open ground. Explain how tree cover keeps the ground under trees warmer.
A 1.0 cm3 air bubble is released from the sandy bottom of a warm, shallow sea, where the gauge pressure is 1.5 atm. The bubble rises slowly enough that the air inside remains at the same constant temperature as the water.a. What is the volume of the bubble as it reaches the surface? b. As the
A tire is inflated to a gauge pressure of 35 psi. The absolute pressure in the tire is A. Less than 35 psi. B. Equal to 35 psi. C. Greater than 35 psi.
A weather balloon rises through the atmosphere, its volume expanding from 4.0 m3 to 12 m3 as the temperature drops from 20°C to -10°C. If the initial gas pressure inside the balloon is 1.0 atm, what is the final pressure?
The number of atoms in a container is increased by a factor of 2 while the temperature is held constant. The pressure A. Decreases by a factor of 4. B. Decreases by a factor of 2. C. Stays the same. D. Increases by a factor of 2. E. Increases by a factor of 4.
A straight rod consists of a 1.2-cm-long piece of aluminum attached to a 2.0-cm-long piece of steel. By how much will the length of this rod change if its temperature is increased from 20°C to 40°C?
A gas is compressed by an isothermal process that decreases its volume by a factor of 2. In this process, the pressure.A. Does not change. B. Increases by a factor of less than 2. C. Increases by a factor of 2. D. Increases by a factor of more than 2.
The length of a steel beam increases by 0.73 mm when its temperature is raised from 22°C to 35°C. What is the length of the beam at 22°C?
A gas is compressed by an adiabatic process that decreases its volume by a factor of 2. In this process, the pressure A. Does not change. B. Increases by a factor of less than 2. C. Increases by a factor of 2. D. Increases by a factor of more than 2.
Older railroad tracks in the U.S. are made of 12-m-long pieces of steel. When the tracks are laid, gaps are left between the sections to prevent buckling when the steel thermally expands. If a track is laid at 16°C, how large should the gaps be if the track is not to buckle when the temperature is
Suppose you do a calorimetry experiment to measure the specific heat of a penny. You take a number of pennies, measure their mass, heat them to a known temperature, and then drop them into a container of water at a known temperature. You then deduce the specific heat of a penny by measuring the
The temperature of an aluminum disk is increased by 120°C. By what percentage does its volume increase?
A cup of water is heated with a heating coil that delivers 100 W of heat. In one minute, the temperature of the water rises by 20°C. What is the mass of the water? A. 72 g C. 720 g B. 140 g D. 1.4 kg
How much energy must be removed from a 200 g block of ice to cool it from 0°C to -30°C?
100 g of ice at 0°C and 100 g of steam at 100°C interact thermally in a well-insulated container. The final state of the system isA. An ice-water mixture at 0°C. B. Water at a temperature between 0°C and 50°C. C. Water at 50°C. D. Water at a temperature between 50°C and 100°C. E. A
Suppose the 600 W of radiation emitted in a microwave oven is absorbed by 250 g of water in a very lightweight cup. Approximately how long will it take to heat the water from 20°C to 80°C?A. 50s B. 100 sC. 150 s D. 200 s
The maximum amount of water an adult in temperate climates can perspire in one hour is typically 1.8 L. However, after several weeks in a tropical climate the body can adapt, increasing the maximum perspiration rate to 3.5 L/h. At what rate, in watts, is energy being removed when perspiring that
Alligators and other reptiles don't use enough metabolic energy to keep their body temperatures constant. They cool off at night and must warm up in the sun in the morning. Suppose a 300 kg alligator with an early- morning body temperature of 25°C is absorbing radiation from the sun at a rate of
When air is inhaled, it quickly becomes saturated with water vapor as it passes through the moist upper airways. When breathing dry air, about 25 mg of water are exhaled with each breath. At 12 breaths/min, what is the rate of energy loss due to evaporation? Express your answer in both watts and
It is important for the body to have mechanisms to effectively cool itself; if not, moderate exercise could easily increase body temperatures to dangerous levels. Suppose a 70 kg man runs on a treadmill for 30 min, using a metabolic power of 1000 W. Assume that all of this power goes to thermal
What minimum heat is needed to bring 100 g of water at 20°C to the boiling point and completely boil it away?
Brewed coffee is often too hot to drink right away. You can cool it with an ice cube, but this dilutes it. Or you can buy a device that will cool your coffee without dilution-a 200 g aluminum cylinder that you take from your freezer and place in a mug of hot coffee. If the cylinder is cooled to
Marianne really likes coffee, but on summer days she doesn't want to drink a hot beverage. If she is served 200 mL of coffee at 80°C in a well-insulated container, how much ice at 0°C should she add to obtain a final temperature of 30°C?
If a person has a dangerously high fever, submerging her in ice water is a bad idea, but an ice pack can help to quickly bring her body temperature down. How many grams of ice at 0°C will be melted in bringing down a 60 kg patient's fever from 40°C to 39°C?
What is the temperature change of 1.0 mol of a monatomic gas if its thermal energy is increased by 1.0 J?
The temperature of 2.0 g of helium is increased at constant volume by ΔT. What mass of oxygen can have its temperature increased by the same amount at constant volume using the same amount of heat?
A 1.8-cm-thick wood floor covers a 4.0 m X 5.5 m room. The subfloor on which the flooring sits is at a temperature of 16.2°C, while the air in the room is at 19.6°C. What is the rate of heat conduction through the floor?
A copper-bottomed kettle, its bottom 24 cm in diameter and 3.0 mm thick, sits on a burner. The kettle holds boiling water, and energy flows into the water from the kettle bottom at 800 W. What is the temperature of the bottom surface of the kettle?
What is the greatest possible rate of energy transfer by radiation from a metal cube 2.0 cm on a side that is at 700°C? Its emissivity is 0.20.
Seals may cool themselves by using thermal windows, patches on their bodies with much higher than average surface temperature. Suppose a seal has a 0.030 m2 thermal window at a temperature of 30°C. If the seal's surroundings are a frosty -10°C, what is the net rate of energy loss by radiation?
What is the greatest possible rate of energy transfer by radiation for a 5.0-cm-diameter sphere that is at 100°C?
Electronics and inhabitants of the International Space Station generate a significant amount of thermal energy that the station must get rid of. The only way that the station can exhaust thermal energy is by radiation, which it does using thin, 1.8-m-by-3.6-m panels that have a working temperature
If you lie on the ground at night with no cover, you get cold rather quickly. Much of this is due to energy loss by radiation. At night in a dry climate, the temperature of the sky can drop to -40°C. If you are lying on the ground with thin clothing that provides little insulation, the surface
A 15-cm-diameter compressed-air tank is 50 cm tall. The pressure at 20°C is 150 atm.a. How many moles of air are in the tank? b. What volume would this air occupy at STP?
A 10-cm-diameter cylinder of helium gas is 30 cm long and at 20°C. The pressure gauge reads 120 psi. a. How many helium atoms are in the cylinder? b. What is the mass of the helium?
Party stores sell small tanks containing 30 g of helium gas. If you use such a tank to fill 0.010 m3 foil balloons (which don't stretch, and so have an internal pressure that is very close to atmospheric pressure), how many balloons can you expect to fill?
0.030 mol of an ideal monatomic gas undergoes an adiabatic compression that raises its temperature from 10°C to 50°C. How much work is done on the gas to compress it?
0.15 mol of an ideal monatomic gas undergoes an adiabatic expansion, cooling from 20°C to -10°C. How much work is done by the gas during the expansion?
Susan, whose mass is 68 kg, climbs 59 m to the top of the Cape Hatteras lighthouse. a. During the climb, by how much does her potential energy increase? b. For a typical efficiency of 25%, what metabolic energy does she require to complete the climb? c. When exercising, the body must perspire
A 68 kg woman cycles at a constant 15 km/h. All of the metabolic energy that does not go to forward propulsion is converted to thermal energy in her body. If the only way her body has to keep cool is by evaporation, how many kilograms of water must she lose to perspiration each hour to keep her
The top layer of your goose down sleeping bag has a thickness of 5.0 cm and a surface area of 1.0 m2. When the outside temperature is -20°C, you lose 25 Cal/h by heat conduction through the bag (which remains at a cozy 35°C inside). Assume that you're sleeping on an insulated pad that eliminates
Suppose you go outside in your fiber-filled jacket on a windless but very cold day. The thickness of the jacket is 2.5 cm, and it covers 1.1 m2 of your body. The purpose of fiber- or down-filled jackets is to trap a layer of air, and it's really the air layer that provides the insulation. If your
Two thin, square copper plates are radiating energy at the same rate. The edge length of plate 2 is four times that of plate 1. What is the ratio of absolute temperatures T1/T2 of the plates?
A drop of green ink falls into a beaker of clear water. First describe what happens. Then explain the outcome in terms of entropy.
If you hold a rubber band loosely between two fingers and then stretch it, you can tell by touching it to the sensitive skin of your forehead that stretching the rubber band has increased its temperature. If you then let the rubber band rest against your fore- head, it soon returns to its original
In areas in which the air temperature drops very low in the winter, the exterior unit of a heat pump designed for heating is sometimes buried underground in order to use the earth as a thermal reservoir. Why is it worthwhile to bury the heat exchanger, even if the underground unit costs more to
A heat engine does 20 J of work while exhausting 30 J of waste heat. What is the engine's efficiency?
When the sun's light hits the earth, the temperature rises. Is there an entropy change to accompany this transformation? Explain.
When you put an ice cube tray filled with liquid water in your freezer, the water eventually becomes solid ice. The solid is more ordered than the liquid-it has less entropy. Explain how this transformation is possible without violating the second law of thermodynamics.
A company markets an electric heater that is described as 100% efficient at converting electric energy to thermal energy. Does this violate the second law of thermodynamics?
A person is walking on level ground at constant speed. What energy transformation is taking place? A. Chemical energy is being transformed to thermal energy. B. Chemical energy is being transformed to kinetic energy. C. Chemical energy is being transformed to kinetic energy and thermal
Converting sunlight to electricity with solar cells has an efficiency of ≈15%. It's possible to achieve a higher efficiency. (though currently at higher cost) by using concentrated sunlight as the hot reservoir of a heat engine. Each dish in Figure P11.30 concentrates sunlight on one side of a
A newly proposed device for generating electricity from the sun is a heat engine in which the hot reservoir is created by focusing sunlight on a small spot on one side of the engine. The cold reservoir is ambient air at 20°C. The designer claims that the efficiency will be 60%. What minimum
A refrigerator takes in 20 J of work and exhausts 50 J of heat. What is the refrigerator's coefficient of performance?
The thermal energy of a container of helium gas is halved. What happens to the temperature, in kelvin? A. It decreases to one-fourth its initial value. B. It decreases to one-half its initial value. C. It stays the same. D. It increases to twice its initial value.
Air conditioners are rated by their coefficient of performance at 80F inside temperature and 95°F outside temperature. An efficient but realistic air conditioner has a coefficient of performance of 3.2. What is the maximum possible coefficient of performance?
An inventor approaches you with a device that he claims will take 100 J of thermal energy input and produce 200 J of electricity. You decide not to invest your money because this device would violate. A. The first law of thermodynamics. B. The second law of thermodynamics. C. Both the first and
Find the maximum possible coefficient of performance for a heat pump used to heat a house in a northerly climate in winter. The inside is kept at 20°C while the outside is -20°C.
For how long would a 68 kg athlete have to swim at a fast crawl to use all the energy available in a typical fast-food meal of burger, fries, and a drink?
To a good approximation, the only external force that does work on a cyclist moving on level ground is the force of air resistance. Suppose a cyclist is traveling at 15 km/h on level ground. Assume he is using 480 W of metabolic power. a. Estimate the amount of power he uses for forward
The winning time for the 2005 annual race up 86 floors of the Empire State Building was 10 min and 49 s. The winner's mass was 60 kg. a. If each floor was 3.7 m high, what was the winner's change in gravitational potential energy?b. If the efficiency in climbing stairs is 25%, what total energy
A 68 kg hiker walks at 5.0 km/h up a 7% slope. What is the necessary metabolic power?
A 70 kg student consumes 2500 Cal each day and stays the same weight. One day, he eats 3500 Cal and, wanting to keep from gaining weight, decides to "work off" the excess by jumping up and down. With each jump, he accelerates to a speed of 3.3 m/s before leaving the ground. How many jumps must he
To make your workouts more productive, you can get a generator that you drive with the rear wheel of your bicycle when it is mounted in a stand. a. Your laptop charger uses 75 W. What is your body's metabolic power use while running the generator to power your laptop charger, given the typical
The resistance of an exercise bike is often provided by a generator; that is, the energy that you expend is used to generate electric energy, which is then dissipated. Rather than dissipate the energy, it could be used for practical purposes. a. A typical person can maintain a steady energy
Larger animals use proportionately less energy than smaller animals; that is, it takes less energy per kg to power an elephant than to power a human. A 5000 kg African elephant requires about 70,000 Cal for basic needs for one day. a. If a 68 kg human required the same energy per kg of body mass
Smaller mammals use proportionately more energy than larger mammals; that is, it takes more energy per gram to power a mouse than a human. A typical mouse has a mass of 20 g and, at rest, needs to consume 3.0 Cal each day for basic body processes. a. If a 68 kg human used the same energy per kg of
A large horse can perform work at a steady rate of about 1 horsepower, as you might expect. a. Assuming a 25% efficiency, how many Calories would a horse need to consume to work at 1.0 hp for 1.0 h? b. Dry hay contains about 10 MJ per kg. How many kilograms of hay would the horse need to eat to
A college student is working on her physics homework in her dorm room. Her room contains a total of 6.0 × 1026 gas molecules. As she works, her body is converting chemical energy into thermal energy at a rate of 125 W. If her dorm room were an isolated system (dorm rooms can certainly feel like
Describe the energy transfers and transformations that occur from the time you sit down to breakfast until you've completed a fast bicycle ride.
A 60% efficient device uses chemical energy to generate 600 J of electric energy.a. How much chemical energy is used? b. A second device uses twice as much chemical energy to generate half as much electric energy. What is its efficiency?
A 10% efficient engine accelerates a 1500 kg car from rest to 15 m/s. How much energy is transferred to the engine by burning gasoline?
Rub your hands together vigorously. What happens? Discuss the energy transfers and transformations that take place.
Figure Q9.21 shows two blocks sliding on a frictionless surface. Eventually the smaller block overtakes the larger one, collides with it, and sticks. What is the speed of the two blocks after the collision? A. vi/2 B. 4vi/5 C. ViD. 5vi/4E. 2vi FIGURE Q9.21 m 2v₁ 3м

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