The coefficient of static friction between a brick and a wooden board is 0.40, and the coefficient of kinetic friction between the brick and board is 0.30. You place the brick on the board and slowly lift one end of the board off the ground until the brick starts to slide down the board. (a) What angle does the board make with the ground when the brick starts to slide? (b) What is the acceleration of the brick as it slides down the board?
> An engine has a 30.0% efficiency. The engine raises a 5.00 kg crate from rest to a vertical height of 10.0 m, at which point the crate has a speed of 4.00 m/s. How much heat input is required for this engine?
> How many grams of carbohydrate does a person of mass 74 kg need to metabolize to climb five flights of stairs (15 m height increase)? Each gram of carbohydrate provides 17.6 kJ of energy. Assume 10.0% efficiency—that is, 10.0% of the available chemical e
> In Problem 6, what is the pile driver’s speed just before it strikes the pile?
> Two engines operate between the same two temperatures of 750 K and 350 K, and have the same rate of heat input. One of the engines is a reversible engine with a power output of 23 kW. The second engine has an efficiency of 42%. What is the power output o
> A certain engine can propel a 1800 kg car from rest to a speed of 27 m/s in 9.5 s with an efficiency of 27%. What are the rate of heat flow into the engine at the high temperature and the rate of heat flow out of the engine at the low temperature?
> The human body could potentially serve as a very good thermal reservoir, as its internal temperature remains quite constant at around 37°C and is stabilized by continual intake of food. Suppose an inventor designed microscopic engines that could be impla
> A model steam engine of 1.00 kg mass pulls eight cars of 1.00 kg mass each. The cars start at rest and reach a velocity of 3.00 m/s in a time of 3.00 s while moving a distance of 4.50 m. During that time, the net heat input is 135 J. What is the change i
> A new organic semiconductor device is able to generate electricity (which can be used to charge a battery or light an LED) using the warmth of human skin. If your skin temperature is maintained by your body at 35°C and the temperature of the surroundings
> (a) Find the heat flow into or out of the gas during each step, (b) Find the entropy change of the gas during the isothermal step. (c) What is the entropy change of the gas for a complete cycle? Is it equal in magnitude to the entropy change of the envir
> The motor that drives a refrigerator produces 148 W of useful power. The hot and cold temperatures of the heat reservoirs are 20.0°C and −5.0°C. What is the maximum possible amount of ice it can produce in 2.0 h from water that is initially at 8.0°C?
> (a) Calculate the work done by the engine during each step and the net work done per cycle. (b) If the heat input per cycle is 58.3 kJ, what is the efficiency?
> The outdoor temperature on a winter's day is −4°C. If you use 1.0 kJ of electric energy to run a heat pump, how much heat does that put into your house at 21°C? Assume that the heat pump is ideal.
> A crate of oranges weighing 180 N rests on a flatbed truck 2.0 m from the back of the truck. The coefficients of friction between the crate and the bed are μs = 0.30 and μk = 0.20. The truck drives on a straight, level highway at a constant 8.0 m/s. (a)
> Estimate the average blood pressure in a person’s foot if the foot is 1.37 m below the aorta, where the average blood pressure is 104 mmHg. For the purposes of this estimate, assume the blood isn’t flowing.
> You need to move a heavy crate by sliding it across a smooth floor. The coefficient of sliding friction is 0.2. You can either push the crate horizontally or pull the crate using an attached rope. When you pull on the rope, it makes a 30° angle with the
> Draw a PV diagram to illustrate the cycle for this engine. Label the axes with numerical values.
> An ideal refrigerator keeps its contents at 0.0°C and exhausts heat into the kitchen at 40.0°C. For every 1.0 kJ of work done, (a) how much heat is exhausted? (b) How much heat is removed from the contents?
> (a) Find the heat flow into or out of the gas during each of the four steps. (b) What is the net heat flow into the gas per cycle? (c) Calculate the change in entropy of the cold reservoir (not of the gas) in steps B and C and the change in entropy of
> At a tea party, a coffeepot and a teapot are placed on the serving table. The coffeepot is a shiny silver-plated pot with emissivity of 0.12; the teapot is ceramic and has an emissivity of 0.65. Both pots hold 1.00 L of liquid at 98°C when the party begi
> Find the change in internal energy of the gas during each of the four steps.
> A black wood stove has a surface area of 1.20 m2 and a surface temperature of 175°C. What is the net rate at which heat is radiated into the room? The room temperature is 20°C.
> (a) Find the work done by the engine during each of the four steps and the net work done for the cycle. (b) If the heat input per cycle is 2770 J, what is the efficiency of the engine? (c) Compare the efficiency to that of an ideal engine using the sam
> If the maximum intensity of radiation for a blackbody is found at 2.65 um, what is the temperature of the blackbody?
> A fish at a pressure of 1.1 atm has its swim bladder inflated to an initial volume of 8.16 mL. If the fish starts swimming horizontally, its temperature increases from 20.0°C to 22.0°C as a result of the exertion. (a) Since the fish is still at the same
> An IV is connected to a patient’s vein. The blood in the vein has a gauge pressure of 12 mmHg. At least how far above the vein must the IV bag be hung in order for fluid to flow into the vein? Assume the fluid in the IV has the same density as blood.
> In a movie, a stuntman places himself on the vertical front of a truck as the truck accelerates. The coefficient of friction between the stuntman and the truck is 0.65. The stuntman is not standing on anything but can “stick” to the front of the truck as
> An incandescent lightbulb radiates at a rate of 60.0 W when the temperature of its filament is 2820 K. During a brownout (temporary drop in line voltage), the power radiated drops to 58.0 W. What is the temperature of the filament? Ignore changes in the
> Mitch drops a 2.0 g coin into a 3.0 m deep wishing well. What is the de Broglie wavelength of the coin just before it hits the bottom of the well?
> Three types of sigma baryons can be created in accelerator collisions. Their quark contents are given by uus, uds, and dds, respectively. What are the electric charges of each of these sigma particles, respectively?
> A reversible heat engine has an efficiency of 33.3%, removing heat from a hot reservoir and rejecting heat to a cold reservoir at 0°C. If the engine now operates in reverse, how long would it take to freeze 1.0 kg of water at 0°C, if it operates on a pow
> A lizard of mass 3.0 g is warming itself in the bright sunlight. It casts a shadow of 1.6 cm2 on a piece of paper held perpendicularly to the Sun's rays. The intensity of sunlight at Earth is 1.4 × 103 W/m2, but only half of this energy penetrates the at
> A container holding 1.20 kg of water at 20.0°C is placed in a freezer that is kept at −20.0°C. The water freezes and comes to thermal equilibrium with the interior of the freezer. What is the minimum amount of electrical energy required by the freezer to
> Consider the net rate of heat loss by radiation from exposed skin on a cold day. By what factor does the rate for an outdoor temperature of 0°C exceed the rate at 5°C? Assume an initial skin temperature of 35°C.
> For a more realistic estimate of the maximum coefficient of performance of a heat pump, assume that a heat pump takes in heat from the outdoors at 10°C below the ambient outdoor temperature, to account for the temperature difference across its heat excha
> It is often argued that the head is the most important part of the body to cover when out in cold weather. Estimate the total energy loss by radiation if a person's head is uncovered for 15 min on a very cold, −15°C day, assuming he is bald, his skin tem
> A manometer using oil (density 0.90 g/cm3) as a fluid is connected to an air tank. Suddenly the pressure in the tank increases by 7.4 mmHg. (a) By how much does the fluid level rise in the side of the manometer that is open to the atmosphere? (b) What
> Estimate the entropy change of 850 g of water when it is heated from 20.0°C to 50.0°C. [Hint: Assume that the heat flows into the water at an average temperature of 35.0°C.]
> A pilot starting from Athens, New York, wishes to fly to Sparta, New York, which is 320 km from Athens in the direction 20.0° north of east. The pilot heads directly for Sparta and flies at an airspeed of 160 km/h. After flying for 2.0 h, the pilot expec
> A student in a lecture hall has 0.25 m2 of skin (arms, hands, and head) exposed. The skin is at 34°C and has an emissivity of 0.97. The temperature of the room is 20°C (air, walls, ceiling, and floor all at the same temperature). (a) At what rate does t
> (a) What is the entropy change of 1.00 mol of H2O when it changes from ice to water at 0.0°C? (b) If the ice is in contact with an environment at a temperature of 10.0°C, what is the entropy change of the universe when the ice melts?
> A student wants to lose some weight. He knows that rigorous aerobic activity uses about 700 kcal/h (2900 kJ/h) and that it takes about 2000 kcal per day (8400 kJ) just to support necessary biological functions, including keeping the body warm. He decides
> An object moves in a circle. Is the total work done on the object by external forces necessarily zero? Explain.
> On a hot day, you are in a sealed, insulated room. The room contains a refrigerator, operated by an electric motor. The motor does work at the rate of 250 W when it is running. The refrigerator removes heat from the food storage space at a rate of 450 W
> A person of surface area 1.80 m2 is lying out in the sunlight to get a tan. If the intensity of the incident sunlight is 7.00 × 102 W/m2, at what rate must heat be lost by the person in order to maintain a constant body temperature? (Assume the effective
> Suppose you inhale 0.50 L of air initially at 20°C and 100 kPa pressure. While holding your breath, this air is warmed at constant pressure to 37°C. Treating the air as an ideal diatomic gas, how much heat flows from the body into the air?
> A sphere with a diameter of 80 cm is initially at a temperature of 250°C. If the intensity of the radiation detected at a distance of 2.0 m from the sphere's center is 102 W/m2, what is the emissivity of the sphere?
> An experiment to determine the specific heat of a gas (Chapter 14) makes use of a water manometer attached to a flask. Initially the two columns of water are even. Atmospheric pressure is 1.0 × 105 Pa. After heating the gas, the water levels
> A balloon contains 160 L of nitrogen gas at 25°C and 1.0 atm. How much energy must be added to raise the temperature of the nitrogen to 45°C while allowing the balloon to expand at atmospheric pressure?
> Six wood stoves have total surface areas A and surface temperatures T as given. Rank them in order of the power radiated, from greatest to least. Assume they all have the same emissivity. (a) A = 1.00 m2, T = 227°C (b) A = 1.01 m2, T = 227°C (c) A = 1.0
> Suppose you mix 4.0 mol of a monatomic ideal gas at 20.0°C and 3.0 mol of another monatomic ideal gas at 30.0°C. If the mixture is allowed to reach equilibrium, what is the final temperature of the mixture? [Hint: Use energy conservation.]
> Wien studied the spectral distribution of many radiating bodies to finally discover a simple relation between wavelength and intensity. Use the limited data shown in Fig. 14.17 to find the constant predicted by Wien for the product of wavelength of maxim
> On a day when the temperature is 19°C, a 0.15 kg baseball is dropped from the top of a 24 m tower. After the ball hits the ground, bounces a few times, and comes to rest, approximately how much has the entropy of the universe increased?
> If a blackbody is radiating at T = 1650 K, at what wavelength is the maximum intensity?
> An electron is confined to a one-dimensional box of length L. When the electron makes a transition from its first excited state to the ground state, it emits a photon of energy 0.20 eV. (a) What is the ground-state energy (in electron-volts) of the elec
> (a) How many moles of gas are used in this engine? (b) Calculate the heat flow into or out of the gas in steps AB and CA. (c) Calculate the work done by the gas during each step.
> A brick wall with thermal conductivity κ = 1.3 W/(m·K) is covered completely with a sheet of foam of the same thickness as the brick, but with κ = 0.025 W/(m·K). How is the rate at which heat is conducted through the wall changed by the addition of the f
> UV light with a wavelength of 180 nm is incident on a metal and electrons are ejected. Instead of determining the maximum kinetic energy of the electrons with a stopping potential, the maximum kinetic energy is determined by injecting the electrons into
> Many species cool themselves by sweating, because as the sweat evaporates, heat is transferred to the surroundings. A human exercising strenuously has an evaporative heat loss rate of about 650 W. If a person exercises strenuously for 30.0 min, how much
> Five walls of a house have different surface areas, insulation materials, and insulation thicknesses. Rank them in order of the rate of heat flow through the wall, greatest to smallest. Assume the same indoor and outdoor temperatures for each wall. (a) a
> If the temperature surrounding the sunbather in Problem 78 is greater than the normal body temperature of 37°C and the air is still, so that radiation, conduction, and convection play no part in cooling the body, how much water (in liters per hour) from
> A woman of mass 51 kg is standing in an elevator. (a) If the elevator floor pushes up on her feet with a force of 408 N, what is the acceleration of the elevator? (b) If the elevator maintains constant acceleration and is moving at 1.5 m/s as it passes
> One cross-country skier is wearing a down jacket that is 2.0 cm thick. The thermal conductivity of goose down is 0.025 W/(m·K). Her companion on the ski outing is wearing a wool jacket that is 0.50 cm thick. The thermal conductivity of wool is 0.040 W/(m
> A 10.0 g iron bullet with a speed of 4.00 × 102 m/s and a temperature of 20.0°C is stopped in a 0.500 kg block of wood, also at 20.0°C, which is fixed in place. (a) At first all of the bullet's kinetic energy goes into the internal energy of the bullet.
> Find the temperature drop across the epidermis (the outer layer of skin) under these conditions: the rate of heat flow via conduction through a 10.0 cm2 area of the epidermis is 50 mW; the epidermis is 2.00 mm thick and has thermal conductivity 0.45 W/(m
> Five ice cubes, each with a mass of 22.0 g and at a temperature of−50.0°C, are placed in an insulating container. How much heat will it take to change the ice cubes completely into steam?
> A hiker is wearing wool clothing of 0.50 cm thickness to keep warm. Her skin temperature is 35°C and the outside temperature is 4.0°C. Her body surface area is 1.2 m2. (a) If the thermal conductivity of wool is 0.040 W/(m·K), what is the rate of heat co
> When a roller coaster takes a sharp turn to the right, it feels as if you are pushed toward the left. Does a force push you to the left? If so, what is it? If not, why does there seem to be such a force?
> When a mercury manometer is connected to a gas main, the mercury stands 40.0 cm higher in the tube that is open to the air than in the tube connected to the gas main. A barometer at the same location reads 740 mmHg. Determine the absolute pressure of the
> While camping, some students decide to make hot chocolate by heating water with a solar heater that focuses sunlight onto a small area. Sunlight falls on their solar heater, of area 1.5 m2, with an intensity of 750 W/m2. How long will it take 1.0 L of wa
> A copper rod has one end in ice at a temperature of 0°C, the other in boiling water. The length and diameter of the rod are 1.00 m and 2.00 cm, respectively. At what rate in grams per hour does the ice melt? Assume no heat flows out the sides of the rod.
> A hotel room is in thermal equilibrium with the rooms on either side and with the hallway on a third side. The room loses heat primarily through a 1.30 cm thick glass window that has a height of 76.2 cm and a width of 156 cm. If the temperature inside th
> Your hot water tank is insulated, but not very well. To reduce heat loss, you wrap some old blankets around it. With the water at 81°C and the room at 21°C, a thermometer inserted between the outside of the original tank and your blanket reads 36°C. By w
> A locomotive pulls a train of 10 identical cars, on a track that runs east-west, with a force of 2.0 × 106 N directed east. What is the force with which the last car to the west pulls on the rest of the train?
> A satellite is placed in a noncircular orbit about Earth. The farthest point of its orbit (apogee) is 4.0 Earth radii from the center of Earth, while its nearest point (perigee) is 2.0 Earth radii from Earth’s center. If we define the gravitational poten
> A 75 kg block of ice at 0.0°C breaks off from a glacier, slides along the frictionless ice to the ground from a height of 2.43 m, and then slides along a horizontal surface consisting of gravel and dirt. Find how much of the mass of the ice is melted by
> Boiling water in an aluminum pan is being converted to steam at a rate of 10.0 g/s. The flat bottom of the pan has an area of 325 cm2 and the pan's thickness is 3.00 mm. If 27.0% of all heat that is transferred to the pan from the flame beneath it is los
> A 60.0 g piece of ice slides 5.00 m down an icy roof inclined at 27.0° to the horizontal. The magnitude of its acceleration is 4.10 m/s2. All the ice is at 0°C. How much ice melts?
> A wall that is 2.74 m high and 3.66 m long has a thickness composed of 1.00 cm of wood plus 3.00 cm of insulation (with the thermal conductivity approximately of wool). The inside of the wall is 23.0°C and the outside of the wall is at −5.00°C. (a) What
> At the surface of a freshwater lake the pressure is 105 kPa. (a) What is the pressure increase in going 35.0 m below the surface? (b) What is the approximate pressure decrease in going 35 m above the surface? Air at 20°C has density of 1.20 kg/m3.
> Two aluminum blocks are in thermal contact. (a) Are the blocks necessarily in physical contact? Explain. (b) If they have the same temperature, do they necessarily have the same internal energy? Explain. (c) If their internal energies are not equal, i
> A copper rod of length 0.50 m and cross-sectional area 6.0 × 10−2 cm2 is connected to an iron rod with the same cross section and length 0.25 m. One end of the copper is immersed in boiling water and the other end is at the
> A free neutron (i.e., a neutron on its own rather than in a nucleus) is not a stable particle. Its average lifetime is 15 min, after which it decays into a proton, an electron, and an antineutrino. Use the energy- time uncertainty principle [Eq. (28-5)]
> A 3.0 L container of nitrogen gas (N2) and a 5.0 L container of oxygen gas (O2) are both at 20°C and 1.0 atm. (a) Which gas has the larger rms speed? Explain. (b) At what temperature will oxygen gas have the same rms speed as nitrogen when the nitrogen
> Given a slab of material with area 1.0 m2 and thickness 2.0 × 10−2 m, (a) what is the thermal resistance if the material is asbestos? (b) What is the thermal resistance if the material is iron? (c) What is the thermal resistance if the material is copp
> A star's spectrum emits more radiation with a wavelength of 700.0 nm than with any other wavelength. (a) What is the surface temperature of the star? (b) If the star's radius is 7.20 × 108 m, what power does it radiate? (c) If the star is 9.78 ly from
> To pass a physical fitness test, Marcella must run 1.00 km at an average speed of 3.33 m/s. She runs the first 0.500 km at an average of 4.20 m/s. What should be her average speed over the remaining 0.500 km in order to finish with an overall average spe
> A metal rod with a diameter of 2.30 cm and length of 1.10 m has one end immersed in ice at 32.0°F and the other end in boiling water at 212°F. If the ice melts at a rate of 1.32 g every 175 s, what is the thermal conductivity of this metal? What metal co
> A 20.0 g lead bullet leaves a rifle at a temperature of 47.0°C and travels at a speed of 5.00 × 102 m/s until it hits a 6.0 kg block of ice at 0°C that is initially at rest on a frictionless surface. The bullet becomes embedded in the ice. (a) How fast
> (a) What thickness of cork would have the same R-factor as a 1.0 cm thick stagnant air pocket? (b) What thickness of tin would be required for the same R-factor?
> What is the average pressure on the soles of the feet of a standing 90.0 kg person due to the contact force with the floor? Each foot has a surface area of 0.020 m2.
> It requires 17.10 kJ to melt 1.00 × 102 g of urethane [CO2(NH2)C2H5] at 48.7°C. What is the latent heat of fusion of urethane in kJ/mol?
> Compute the heat of fusion of a substance from these data: 31.15 kJ will change 0.500 kg of the solid at 21°C to liquid at 327°C, the melting point. The specific heat of the solid is 0.129 kJ/(kg·K).
> A stainless steel saucepan, with a base that is made of 0.350 cm thick steel [ κ = 46.0 W/(m·K)] fused to a 0.150 cm thickness of copper [κ = 401 W/(m·K)], sits on a ceramic heating element at 104.00°C. The diameter of the pan is 18.0 cm, and it contains
> You are given 250 g of coffee (same specific heat as water) at 80.0°C (too hot to drink). In order to cool this to 60.0°C, how much ice (at 0.0°C) must be added? Ignore the heat capacity of the cup and heat exchanges with the surroundings.
> Explain why the force of gravity due to Earth does not pull the Moon in closer and closer on an inward spiral until it hits Earth’s surface.
> The inner vessel of a calorimeter contains 2.50 × 102 g of tetrachloromethane, CCl4, at 40.00°C. The vessel is surrounded by 2.00 kg of water at 18.00°C. After a time, the CCl4 and the water reach the equilibrium temperature of 18.54°C. What is the speci
> A phase diagram is shown. Starting at point A, follow the dashed line to point E and consider what happens to the substance represented by this diagram as its pressure and temperature are changed. (a) Explain what happens for each line segment, AB, BC,
> A rocket is launched from rest. After 8.0 min, it is 160 km above Earth’s surface and is moving at a speed of 7.6 km/s. Assuming the rocket moves up in a straight line, what are its (a) average velocity and (b) average acceleration?
> On a hot summer day, Daphne is off to the park for a picnic. She puts 0.10 kg of ice at 0°C in a thermos and then adds tea initially at 25°C. How much tea will just melt all the ice?
> A dog loses a lot of heat through panting. The air rushing over the upper respiratory tract causes evaporation and thus heat loss. A dog typically pants at a rate of around 300 pants per minute. As a rough calculation, assume that one pant causes 0.010 g
