Problem 1:
You work at a camp and play the bugle, a simple musical horn with a single brass pipe. Despite having no valves to change the length of that pipe, you can produce several different notes (or pitches) from the bugle to wake everyone up at dawn. What are you doing to change the notes (or pitches) of the bugle?
(A) You are causing the column of air inside the pipe to vibrate in its different vibrational modes, each of which has a different pitch.
(B) You are changing the diameter of the brass pipe and changing the pitch at which it vibrates.
(C) You are changing the mass of the brass pipe and changing the pitch at which it vibrates.
(D) You are changing the tension in the brass pipe and changing the pitch at which it vibrates.
Problem 2:
The plumbing in a new high-rise hotel was carefully designed so that the water pressure is exactly the same on all floors and the bathroom showers spray exactly the same on all floors. Neglecting any effects due to viscosity or friction, the total ordered energy (the sum of gravitational potential energy, pressure potential energy, and kinetic energy) per liter of water is
(A) the same on different floors and the sum of pressure potential energy and kinetic energy per liter is the same on different floors.
(B) the same on different floors and the sum of pressure potential energy and kinetic energy per liter is different on different floors.
(C) different on different floors and the sum of pressure potential energy and kinetic energy per liter is different on different floors.
(D) different on different floors, but the sum of pressure potential energy and kinetic energy per liter is the same on different floors.
Problem 3:
An airplane is cruising at constant velocity, 30,000 feet in the air. Which of the following correctly describes the situation above the airplane's wing?
(A) The airstream over the wing is bending upward, away from the wing, so the pressure just above the wing must be less than the local atmospheric pressure.
(B) The airstream over the wing is traveling straight ahead, so the pressure just above the wing must equal the local atmospheric pressure.
(C) The airstream over the wing is bending downward, toward the wing, so the pressure just above the wing must be less than the local atmospheric pressure.
(D) The airstream over the wing is bending downward, toward the wing, so the pressure just above the wing must be greater than the local atmospheric pressure.
Problem 4:
You are jogging on a hot, humid summer day and are covered with perspiration. Unfortunately, that perspiration doesn't cool you off much because
(A) the air pressure is too high to permit water to evaporate quickly.
(B) the air density is too low to permit water to evaporate quickly.
(C) water molecules are landing from the air onto your perspiration almost as often as they are leaving your perspiration for the air.
(D) the air density is too high to permit water to evaporate quickly.
Problem 5:
An automobile engine "knocks" when the gaseous fuel-air mixture in its cylinder ignites spontaneously rather than waiting for the sparkplug to ignite it. What causes that premature ignition of the fuel-air mixture?
(A) Entropy in the fuel-air mixture becomes thermal energy and ignites the mixture.
(B) Heat flowing into the fuel-air mixture from the engine's walls ignites the mixture.
(C) Expansion of the fuel-air mixture causes its temperature to surge upward so that it ignites.
(D) Compression of the fuel-air mixture causes its temperature to surge upward so that it ignites.
Problem 6:
After preventing a score, the goalie kicks the soccer ball toward midfield. The soccer ball gradually slows down, even though it is travelling almost horizontally. The primary reason for this slowing is that the
(A) air pressure at the front and back of the ball is greater than atmospheric pressure, while the air pressure on the sides of the ball is less than atmospheric.
(B) air pressure at the front of the ball is greater than atmospheric pressure, while the air pressure behind the ball is approximately atmospheric.
(C) air pressure at the front of the ball is equal to atmospheric pressure, while the air pressure behind the ball is less than atmospheric.
(D) air pressure at the front and back of the ball is less than atmospheric pressure, while the air pressure on the sides of the ball is more than atmospheric.
Problem 7:
Increasing the amount of carbon dioxide (a greenhouse gas) in the earth's atmosphere
(A) increases the rate at which the earth radiates heat into space.
(B) decreases the rate at which the earth radiates heat into space.
(C) has no effect on the earth's thermal radiation or the effective surface that emits that thermal radiation.
(D) increases the altitude of the earth's effective radiating surface.
Problem 8:
A satellite is orbiting the Earth at an altitude of 100 miles. The net force on that satellite is
(A) zero and it is not accelerating.
(B) zero, but its velocity is changing as its path bends around the Earth.
(C) equal to its weight and it is accelerating toward the center of the Earth.
(D) zero, but its acceleration is changing as its path bends around the Earth.
Problem 9:
You purchase an antique wall clock that uses a pendulum as its timekeeper. The seller, who lives in Northern Canada truthfully said that the clock keeps perfect time. When you mount it on the wall of your dorm room, where the earth's gravity is slightly weaker, the clock
(A) runs a little slow (causing you to be late for classes).
(B) continues to keep perfect time because the period of a pendulum depends only on its length and not on the strength of gravity.
(C) runs a little fast (causing you to be early for classes).
(D) continues to keep perfect time because the period of a pendulum depends only on its mass and not on the strength of gravity.
Problem 10:
Running on soft dry sand is exhausting, so you switch to running on hard wet sand. The hard wet sand removes less energy from you because it
(A) pushes up on your foot just as hard as your foot pushes down on it, unlike the soft dry sand.
(B) stops the downward motion of your foot faster and thus absorbs less of your momentum.
(C) barely moves downward as you push downward on it, so you do almost zero work on it.
(D) stops the downward motion of your foot faster and thus absorbs more of your momentum.
Problem 11:
The waiting room in a bus station gets cold in winter, so the company has installed an electric heater high on one wall where no one can accidently touch it. When that heater is turned on, it turns electric power directly into thermal power, like an electric toaster. Heat then flows from the heater to people seated on benches near the floor
(A) equally poorly via conduction, convection, and radiation, and the room will remain cold.
(B) primarily via radiation, with almost no heat flowing via conduction or convection.
(C) equally well via conduction, convection, and radiation, and the room will become warm.
(D) primarily via convection and radiation, with almost no heat flowing via conduction.
Problem 12:
You have forgotten to buy more shampoo and there is only a tiny bit left in your old bottle. To move that shampoo toward the opening of the bottle, you swinging the bottle rapidly in a circle with its cap-end pointing away from the center of the circle. This technique works because
(A) centrifugal force pushes the shampoo toward the cap-end of the bottle.
(B) viscous forces push the shampoo toward the cap-end of the bottle.
(C) the force of the shampoo 's momentum pushes it toward the cap-end of the bottle.
(D) the bottle's rapid inward acceleration leaves the shampoo behind so that it moves toward the cap-end of the bottle.
Problem 13:
A bottle in both thermal and phase equilibrium at 0 °C contains 1 kilogram of ice and 1 kilogram of liquid water. You move the bottle to a new location and allow it to reach equilibrium at -0.5 °C. The bottle now contains
(A) 0.5 kilograms of ice and 1.5 kilograms of liquid water.
(B) 2 kilograms of ice.
(C) 1.5 kilograms of ice and 0.5 kilograms of liquid water.
(D) 1 kilogram of ice and 1 kilogram of liquid water.
Problem 14:
When you pull a tablecloth out from under a set of dishes, it's important to pull the cloth as fast as possible because
(A) the force of sliding friction that the cloth exerts on the dishes is proportional to the time during which the cloth is moving.
(B) the work done on the dishes by the cloth is proportional to the time during which the cloth pulls on them.
(C) the momentum transferred to the dishes is proportional to the time during which the cloth pulls on them.
(D) the weight of the dishes on the cloth is proportional to the time during which the cloth is moving.
Problem 15:
Water is flowing gently out of the end of a garden hose. You block off most of the hose's opening with your thumb and now the water sprays out at high speed because you
(A) are keeping air from getting into the hose, where it would reduce the water pressure.
(B) are compressing the water and increasing its density.
(C) are doing work on the water with your thumb and greatly increasing its total energy.
(D) have slowed the water flow through hose and plumbing so that the water wastes less ordered energy doing work against viscous forces.
Problem 16:
A music shop has numerous stringed instruments on display, including violins, guitars, and harps. You pluck the string of one instrument and it emits a tone with a frequency of 440 cycles per second (a pitch known as Concert A). When you stop that string from vibrating, you notice that other strings in the room are now vibrating at 440 cycles per second. Why did this happen?
(A) Energy passed from the string you plucked to all the other strings in the room via universal energy transfer and caused them all to vibrate at 440 cycles per second.
(B) The string you plucked synchronized the vibrations of all the other strings in the room so that they all vibrated together.
(C) Those other strings were also tuned to vibrate at 440 cycles per second and energy was passed gradually from the string you plucked to those other strings via resonant energy transfer.
(D) Your plucking motion caused all of the strings in the room to vibrate at 440 cycles per second, although not nearly as loudly as it caused your string to vibrate.
Problem 17:
A helium-filled balloon weighs only about 1/7th as much as the air it displaces. If you replace the helium gas in the balloon with hydrogen gas (which is half as dense as helium gas), the upward buoyant force on the balloon would
(A) increase and the net force on the balloon would approximately double in the upward direction.
(B) increase and the net force on the balloon would increase slightly in the upward direction.
(C) stay the same and the net force on the balloon would increase slightly in the upward direction.
(D) decrease and the net force on the balloon would approximately double in the upward direction.
Problem 18:
An automobile engine becomes more energy efficient (better gas mileage) as the temperature reached when it burns fuel in air increases (when its flame becomes hotter) because increasing the temperature difference between the hot flame and the cold outdoor air
(A) increases the momentum produced by transferring 1 joule of thermal energy from the flame to the air.
(B) increases the entropy produced by transferring 1 joule of thermal energy from the flame to the air.
(C) decreases the entropy produced by transferring 1 joule of thermal energy from the flame to the air.
(D) decreases the momentum produced by transferring 1 joule of thermal energy from the flame to the air.
Problem 19:
On a hot day, you drink the last drop of water in your plastic water bottle and then seal it closed. As the bottle cools off in your air conditioned car, the bottle's sides bend slightly inward so that the bottle now has slightly less volume than when you sealed it. Since you seal it, the air pressure inside the bottle has
(A) stayed the same, but the density inside the bottle has increased.
(B) stayed the same, but the density inside the bottle has decreased.
(C) decreased and the density inside the bottle has increased.
(D) decreased, but the density inside the bottle has stayed the same.
Problem 20:
If you try to cook vegetables with 100 °C air, it takes a long time. But if you cook those same vegetables with 100 °C steam, they cook quickly. This is because the steam
(A) condenses on the colder vegetables and releases a large amount of heat to the vegetables.
(B) causes moisture inside the vegetables to boil and absorb heat from the vegetables.
(C) condenses on the colder vegetables and absorbs a large amount of heat from the vegetables.
(D) causes moisture inside the vegetables to boil and transfer heat to the vegetables.
Problem 21:
You are studying for final exams in a perfectly insulated and isolated room. Absolutely nothing passes into or out of this room, not even sound, light, electricity, or heat. As you study in this special room,
(A) the entropy (disorder) of the room and its contents is increasing.
(B) the entropy (disorder) of the room and its contents is decreasing.
(C) the energy of the room and its contents is increasing.
(D) the energy of the room and its contents is decreasing.
Problem 22:
You string a zip-line (a taut metal cable) from the balcony of your mansion to the stables 500 meters away. A small trolley allows you to glide down that cable to visit your horses. On a windy day, you notice that the cable is vibrating slightly in its fundamental vibrational mode with a period (time to complete 1 full cycle of motion) of 1 second. What could you do to the cable to decrease (shorten) that period?
(A) Decrease the cable's tension, decrease the cable's mass, or shorten the cable.
(B) Increase the cable's tension, increase the cable's mass, or shorten the cable.
(C) Decrease the cable's tension, decrease the cable's mass, or lengthen the cable.
(D) Increase the cable's tension, decrease the cable's mass, or shorten the cable.
Problem 23:
An air conditioner's compressor takes low density gas and compresses that gas to high density. During this compression process, the gas's
(A) temperature rises and so does its pressure.
(B) temperature drops, but its pressure rises.
(C) temperature stays the same, but its pressure rises.
(D) temperature rises, but its pressure drops.
Problem 24:
In Charlottesville, water boils at approximately 100 °C (212 °F). In the Blue Ridge Mountains, however, water boils at about 97 °C (207 °F) because
(A) 97 °C in the mountains is actually the same temperature as 100 °C in Charlottesville.
(B) the greater altitude in the mountains gives water molecules farther to fall after they break free of the water's surface as steam.
(C) the reduced atmospheric pressure in the mountains allows steam bubbles in the water to grow by evaporation at that lower temperature.
(D) the weaker gravity in the mountains allows water molecules to move faster at that lower temperature.
Problem 25:
Water hammer occurs when you suddenly stop the rapid flow of water in a pipe and results in the pipe-end experience a huge force in the direction of the water's original motion. It happens because flowing water has
(A) acceleration.
(B) energy.
(C) angular momentum.
(D) momentum.
Problem 26:
The curator (artistic director) of a museum's gallery has laid a wool rug on a stone block and placed a copper vase on the rug. That gallery has a uniform temperature throughout, including all of the objects it contains. As a result of contact between those three objects, heat
(A) flows from the copper pot to wool rug, and from the stone block to the wool rug.
(B) flows from the wool rug to the copper pot, and from the wool rug to the stone block.
(C) does not flow at all.
(D) flows from the copper vase to wool rug, and from the wool rug to the stone block.
Problem 27:
To avoid tipping over while turning right on a bicycle, why must you lean the bicycle toward your right?
(A) You accelerate rightward as you turn right and your inertia tends to make you tip over toward your left. By leaning toward your right, you cancel that tendency and avoid tipping over.
(B) Leaning the bicycle decreases the downward force that the ground exerts on its wheels and reduces your downward acceleration.
(C) Leaning the bicycle increases the upward force that the ground exerts on its wheels and reduces your downward acceleration.
(D) Leaning the bicycle reduces the frictional force that the ground exerts on its wheels and reduces its tendency to tip over during the turn.
Problem 28:
You are standing in the middle of a subway car that is moving forward at constant velocity when another passenger accidently spills an enormous container of olive oil. Suddenly, the floor cannot exert any frictional forces on your feet. Nothing else is touching you, so you
(A) shift toward the side of the subway car (perpendicular to the direction of its velocity).
(B) remain in the middle of the subway car.
(C) shift toward the front of the subway car (in the direction of its velocity).
(D) shift toward the back of the subway car (opposite its velocity).
Problem 29:
The energy needed to operate an air conditioner during the summer decreases as the outdoor temperature becomes less hot and as you adjust the thermostat to let the indoor air become less cold. The air conditioner needs less electric energy to move each joule of heat from indoor air to outdoor air because, as the temperature difference between the cool indoor air and the warm outdoor air decreases,
(A) less thermal energy must become ordered energy to make up for the entropy lost when heat moves against its natural direction of flow.
(B) less thermal energy must become ordered energy to make up for the entropy produced when heat moves against its natural direction of flow.
(C) less ordered energy must become thermal energy to make up for the entropy lost when heat moves against its natural direction of flow.
(D) less ordered energy must become thermal energy to make up for the entropy produced when heat moves against its natural direction of flow.
Problem 30:
You and several friends take turns bungee jumping from Beta Bridge, using the same spring-like bungee cord. Near the end of your turn, you bounce gently up and down on the cord with a period (the time it takes for each bounce) of 1 second. One friend has your same height, but is heavier than you. Another friend has your same weight, but is shorter than you. During your friends' turns, what are the periods of their bounces?
(A) Your heavier friend has a period longer than 1 second, your shorter friend has a period longer than 1 second.
(B) Your heavier friend has a period longer than 1 second, your shorter friend has a period of 1 second.
(C) Your heavier friend has a period of 1 second, your shorter friend has a period longer than 1 second.
(D) Your heavier friend has a period of 1 second, your shorter friend has a period shorter than 1 second.
Problem 31:
You are competing in an "egg toss" event in which pairs of people toss raw eggs back and forth at gradually increasing distances. The winning pair is the one that tosses the egg the greatest distance without breaking it. To catch your egg without breaking it, you must allow that egg to push your hands a long distance in the direction of its velocity, a pushing process that takes a long period of time. Allowing your hands to move with the egg in this manner is crucial because it allows your hands to
(A) extract both the egg's kinetic energy and the egg's forward momentum while exerting only small forces on the egg.
(B) extract the egg's kinetic energy while exerting only small forces on it, but leaves the egg's forward momentum unchanged.
(C) convert both the egg's kinetic energy and the egg's forward momentum into entropy in your hand.
(D) extract the egg's forward momentum while exerting only small forces on it, but leaves the egg's kinetic energy unchanged.
Problem 32:
As heat flows from hot soup to a cold kitchen, the entropy (disorder) of the soup
(A) increases, the entropy of the kitchen decreases, and their combined entropy remains unchanged.
(B) decreases, the entropy of the kitchen increases, and their combined entropy increases.
(C) increases, the entropy of the kitchen decreases, and their combined entropy increases.
(D) decreases, the entropy of the kitchen increases, and their combined entropy remains unchanged.
Problem 33:
You are inflating a shiny plastic balloon with helium. The balloon starts as a thin, flat bag but it gradually gets thicker as it fills. At first, the thin plastic balloon doesn't float. But as you keep adding helium to the balloon and it gets thicker, it eventually begins floating because
(A) the helium-filled balloon's weight decreases as you put more lightweight helium particles inside it and eventually it becomes weightless.
(B) the average pressure of the helium-filled balloon increases as it fills and its pressure eventually becomes greater than that of the air it displaces.
(C) the upward buoyant force on a balloon full of helium is larger than the buoyant force on an identical balloon full of air.
(D) the weight of the helium-filled balloon increases as it fills, but the buoyant force it experiences increases much faster and eventually the buoyant force exceeds the balloon's weight.
Problem 34:
A gust of wind shakes your home and causes a hanging chandelier to begin swinging gently back and forth on its support chain. When its overall motion is small, the time it takes the chandelier to complete one full oscillation of that motion (its period of oscillation) does not depend on
(A) the chandelier's amplitude of motion, but it does depend on the chandelier's weight.
(B) the length of the chain supporting the chandelier.
(C) the chandelier's weight, but it does depend on the chandelier's amplitude of motion.
(D) either the chandelier's weight or the chandelier's amplitude of motion.
Problem 35:
A racecar is driving around a circular track at a steady speed of 100 mph (160 km/h). The net force on the racecar is
(A) directed toward the center of the track.
(B) zero.
(C) directed along the racecar's velocity (along its direction of travel).
(D) directed away from the center of the track.
Problem 36:
A hot air balloon is passing over your head when the pilot turns on the flame and heats up the air inside the balloon's envelope (the balloon's fabric skin). That envelope is open at the bottom, where the flame heats it. As the temperature of the air inside the unsealed envelope increases, the
(A) air molecules flow into the envelope's opening and the pressure of the air inside the envelope increases.
(B) air molecules flow out of the envelope's opening and the weight of the air inside the envelope decreases.
(C) air molecules flow into the envelope's opening and the density of the air inside the envelope increases.
(D) upward buoyant force on the balloon increases and it begins to rise.
Problem 37:
The three nonflammable objects in your hand are identical except that one is black, one is white, and one is shiny. You place them in a roaring fire and soon they have the same temperature: 1800 °C. They remain solid. Which one is glowing most brightly?
(A) The object that originally appeared white.
(B) The object that originally appeared silver.
(C) They are all glowing with equal brightness.
(D) The object that original appeared black.
Problem 38:
You drop a bag of flour onto a trampoline and the bag rebounds upward almost to its original height. Compare the bag's energy and momentum just before it bounced on the trampoline with its energy and momentum just after bounced off the trampoline.
(A) The bag's energy changed significantly, but its momentum changed only a little.
(B) The bag's energy changed only a little, but its momentum changed significantly.
(C) The bag's energy and momentum changed only a little.
(D) The bag's energy and momentum changed significantly.
Problem 39:
How is a steam engine able to obtain work (ordered energy) from hot steam?
(A) The hot steam has a large amount of momentum and that momentum can be converted into work.
(B) The steam's thermal energy can be converted into work because both are energy and energy is conserved.
(C) As heat flows from the hot steam to the colder environment, the steam engine is able to divert a fraction of that heat and convert it into work.
(D) The hot steam has a large amount of entropy and that entropy can be converted into work.
Problem 40:
When you jump while standing on a bathroom scale, it briefly reads more than your actual weight. During that moment, it is exerting an upward force on you that is
(A) equal to your weight and you are accelerating upward.
(B) equal to your weight and your velocity is constant.
(C) greater than your weight and your velocity is constant.
(D) greater than your weight and you are accelerating upward.
Problem 41:
Your friend puts an open container of vegetable soup in a frost-free freezer and lets it freeze solid. He then forgets about it for more than year. We he rediscovers the open container, he finds it almost empty except for the vegetables because
(A) the soup has melted periodically and some of it has dripped into the bottom of the freezer.
(B) the greedy vegetables drank the soup.
(C) the soup has melted periodically and some of it has evaporated before it could refreeze.
(D) the soup's water molecules have gone directly from solid ice to gaseous water vapor.
Problem 42:
When the A-string of a guitar vibrates in its fundamental mode without anyone touching it, it has a frequency (or pitch) of 110 cycles per second. When that same string is vibrating at 330 cycles per second without anyone touching it, it is vibrating in it
(A) fundamental mode, but traveling 1/3rd as far during each vibrational cycle.
(B) third harmonic mode, as three 1/3rd-length strings.
(C) fundamental mode, but traveling 3 times as far during each vibrational cycle.
(D) fundamental mode just as before, but completing the same motion 3 times as quickly.
Problem 43:
When a liquid flows through a collection of stationary obstacles, its flow can be smooth and laminar, or it can be swirling and turbulent. The liquid's flow is more likely to become turbulent if you increase its
(A) speed or its density.
(B) speed or its viscosity.
(C) viscosity or its density.
(D) pressure.
Problem 44:
It's a snowy day and you are pulling your sled up a hill. Both you and the sled are moving at constant velocity. The net force on you is
(A) zero and the net force on the sled is zero.
(B) directed uphill and the net force on the sled is directed downhill.
(C) directed uphill and the net force on the sled is directed uphill.
(D) directed downhill and the net force on the sled is directed uphill.
Problem 45:
The characteristic of a harmonic oscillator that makes it especially suitable for use as a timekeeper in a clock is that its
(A) period of oscillation does not depend on its amplitude (extent of motion).
(B) momentum is constant throughout its oscillation.
(C) amplitude (extent of motion) is constant, regardless of its total energy.
(D) total energy is constant, regardless of its amplitude (extent of motion).
Problem 46:
Near sea level, water normally boils at about 100 °C (212 °F). However, a microwave oven can heat water in a glass container above that temperature if
(A) no initial steam bubbles form within the liquid water.
(B) the glass container does not conduct electricity.
(C) the glass container remains colder than 100 °C (212 °F).
(D) the water is very pure.
Problem 47:
When water flows around a bend in a garden hose, the water pressure
(A) decreases near the inside of the curve and decreases near the outside of the curve.
(B) increases near the inside of the curve and decreases near the outside of the curve.
(C) decreases near the inside of the curve and increases near the outside of the curve.
(D) increases near the inside of the curve and increases near the outside of the curve.
Problem 48:
Modern double-pane windows provide excellent thermal insulation. The inner surface of one of those panes is coated with a transparent electrical conductor because that coating
(A) attracts gas atoms and thereby limits convective heat transfer by the argon gas trapped between the panes.
(B) improves the thermal conductivity of the coated pane and helps keep it at the same temperature as the other pane.
(C) reflects infrared light and blocks radiative heat transfer from one pane to the other.
(D) prevents the argon gas atoms from transferring heat via conduction to the coated pane.
Problem 49:
A rocket designed to put a satellite in orbit around the earth has two main tasks. First, it must lift the satellite above earth's atmosphere to eliminate air resistance. Second, it must
(A) give the satellite such a large upward vertical speed that the falling satellite cannot descend to the ground.
(B) push upward on the satellite with a force that balances the satellite's downward weight so that the satellite can coast at constant velocity.
(C) give the satellite such a large sideways acceleration that the satellite's apparent weight is zero.
(D) give the satellite such a large horizontal speed that the falling satellite arcs endlessly around the earth rather than descending to the ground.
Problem 50:
A friend suggests that you invest in a new invention that supposedly absorbs heat from the room and converts it into electricity. According to a brochure, the device sits in the middle of the room, gradually cooling the room air while providing a steady and endless supply of electric power. You wisely choose not to invest in the device because in order to work as described, it would have to do something impossible-it would have to
(A) violate the conservation of energy.
(B) lower the world's total entropy.
(C) turn work into heat, or more precisely, into thermal energy.
(D) turn stored energy into power.
Problem 51:
The air conditioner in your home is cooling the indoor air on a hot summer. As that electric air conditioner operates, what happens to the energy of the indoor air, the outdoor air, and the electric company?
(A) The energies of the indoor air and the electric company decrease, and the energy of the outdoor air increases.
(B) The energies of the indoor air and the outdoor air decrease, and the energy of the electric company increases.
(C) The energies of the outdoor air and the electric company decrease, and the energy of the indoor air increases.
(D) The energies of the indoor air and the outdoor air increase, and the energy of the electric company decreases.
Problem 52:
The flow of air around a ball can be perfectly laminar only when the ball is traveling extremely slowly through the air. During such laminar flow, the ball experiences
(A) both viscous drag and pressure drag.
(B) pressure drag but not viscous drag.
(C) viscous drag but not pressure drag.
(D) neither viscous drag nor pressure drag.
Problem 53:
When you light a candle, its flame turns wax molecules and oxygen into water and carbon dioxide molecules. The molecules that form during this combustion have
(A) less chemical momentum than the original wax and oxygen molecules.
(B) less chemical potential energy than the original wax and oxygen molecules.
(C) more chemical momentum than the original wax and oxygen molecules.
(D) more chemical potential energy than the original wax and oxygen molecules.
Problem 54:
At takeoff, an airplane tilts its wings so that the leading edge (front portion of the wing) is higher than the trailing edge (back portion of the wing) and thereby obtains enough upward lift force to rise into the sky. The more aggressively it tilts its wings (the greater its angle of attack), the more lift it obtains and the faster it rises. There is a limit, however, to the rate at which the airplane can rise. If its angle of attack is too great, what happens?
(A) The airplane's engines can no longer provide enough thrust to keep the plane moving forward.
(B) Beyond a certain angle of attack, the lift becomes constant, regardless of the angle.
(C) The wings become blunt objects and they stall (they produce large turbulent wakes).
(D) The airplane completes a loop-the-loop instead of rising upward.
Problem 55:
Goose down is the soft, fluffy feathers near a goose's skin. The reason that a goose down jacket keeps you so warm in the winter is that
(A) goose down's white coloring assists the radiative transfer of heat from the outer surface of the coat to your skin.
(B) goose down's low average density reduces its buoyant force.
(C) the fine structure of the goose down traps air and prevents it from undergoing convection.
(D) the fibrous material in goose down is a poorer conductor of heat than the air it displaces.
Problem 56:
Two identical rooms at identical temperatures contain identical collections of atoms. In one room that collection consists of a block of salt and a basin of fresh water. In the other room that collection consists of a basin of salt water. Which of the two rooms has the greater entropy (disorder)?
(A) The two rooms have equal entropies because they contain identical collections of atoms.
(B) The two rooms have equal entropies because they have identical temperatures.
(C) The room containing the block of salt and the basin of fresh water has the greater entropy.
(D) The room containing the salt water has the greater entropy.
Problem 57:
A large hot air balloon drifts horizontally with the wind. What causes the balloon's velocity to change when the wind's velocity changes? [For simplicity, neglect any vertical motions of the balloon or wind.]
(A) The wind exerts a buoyant force on the balloon, pushing the balloon in the direction of the wind.
(B) The force of the balloon's momentum always points in the direction of the wind, so it adjusts automatically to changes in the wind.
(C) Whenever the two velocities are different, the wind exerts a pressure drag force on the balloon and the balloon accelerates until its velocity is that of the wind.
(D) The balloon's weight always pushes the balloon downwind, so that the balloon accelerates in the direction of the wind's velocity.
Problem 58:
An toddler's sipping cup has a round base (like the bottom half of a ball) that is weighed so that the cup always returns to upright after being tipped. The cup is in a stable equilibrium when it is upright and tipping it causes its total
(A) kinetic energy to increase.
(B) potential energy to decrease.
(C) potential energy to increase.
(D) kinetic energy to decrease.
Problem 59:
A dozen houses have just been built on a steep hillside overlooking a beautiful lake. A simple water distribution system provides water to all of those houses; they share a single delivery pipe with a branch for each house. Residents at various altitudes above the lake begin taking showers and have different experiences. They observe that the total ordered energy per liter in the spraying water is (neglecting any effects of viscosity and friction)
(A) greater at higher altitudes.
(B) the same on all altitudes, but the speed of the spraying water is greater at higher altitudes.
(C) the same at all altitudes, but the speed of the spraying water is smaller at higher altitudes.
(D) smaller at higher altitudes.
Problem 60:
As an orchestra warms up, the wind instruments (e.g., flutes, clarinets, oboes) and the air inside them actually become hotter. These instruments have openings and are not sealed. How does this warming process affect the average pressure and density of the air inside the wind instruments?
(A) The average pressure does not change, but the average density decreases.
(B) The average pressure decreases, but the average density does not change.
(C) The average pressure does not change, but the average density increases.
(D) The average pressure increases, but the average density does not change.