Physics Final

As water flows downward in a vertical pipe that has a uniform diameter, the water's gravitational potential energy decreases,

its pressure potential energy increases, but its kinetic energy remains constant.

You are riding a motorcycle at constant velocity along a horizontal road while wearing a heavy leather jacket. As you cruise down road, you are doing

zero work on the jacket and it is doing zero work on you.

You are waterskiing at constant velocity on a calm lake while wearing a lifejacket. As you move across the water, you are doing

zero work on the jacket and it is doing zero work on you.

You are an astronaut floating in empty space far from Earth or anything else. You throw a wrench forward as hard as you can. While that wrench is moving forward at great speed, the net force on that wrench is

zero.

You are in a spaceship far from earth and you fire a cannonball into frictionless, empty space. While the cannonball travels forward through space at enormous speed, the net force on that cannonball is

zero.

You are pulling your niece uphill on a sled and the sled experiences a small downhill frictional force as it slides uphill on the snow. Your niece is traveling in a straight line at a constant speed. The net force your niece is experiencing is

zero.

The characteristic of a harmonic oscillator that makes it especially suitable for use as a timekeeper in a clock is that

its period of oscillation does not depend on its amplitude (extent of motion).

If you're trying to increase the pressure in the water distribution system by modifying the local water tower, you should make the water tower

taller.

Firefighters are battling a fire on the 12th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the steady stream of water up to the 10th floor. So they carry the end of the same fire hose up a 2-story-tall ladder and shoot water upward. The other end of the hose remains attached to the same water source as before. Now the steady stream of water rises to the

10th floor.

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

2 kilograms of ice.

A space-walking astronaut in orbit around the earth has a weight of 600 newtons. This means that the earth exerts a downward force of 600 newtons on the astronaut. How much upward force does she exert on the earth?

600 newtons.

Firefighters are battling a fire on the 10th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the steady stream of water up to the 8th floor. So they carry the end of the same fire hose up a 2-story-tall ladder and shoot water upward. The other end of the hose remains attached to the same water source as before. Now the steady stream of water rises to the

8th floor.

Which of the following systems is definitely not a harmonic oscillator?

A bouncy ball bouncing up and down above a granite tabletop.

A silver flute produces a tone as the flautist blows across a hole near the end of the flute. What is vibrating to produce this tone?

A column of air inside the flute is vibrating along its length.

You are rearranging the game room in your mansion and are now pushing the pool table forward across the floor. The floor is exerting a backward frictional force of 200 newtons on the table as the table moves directly forward at a constant speed. What force are you exerting on the table?

A forward force of 200 newtons.

Which of the following is a harmonic oscillator?

A mass with a stable equilibrium that experiences a restoring force that is proportional to its displacement from equilibrium.

You are trying to win a prize at the state fair by knocking a massive can off a shelf. You have a choice of 4 different objects to throw at the can, each with a mass of 1 kg. With which of the following objects are you most likely to win?

A stiff bouncy ball.

You find three open mugs in the kitchen: one filled with boiling water at 212 °F (100 °C), the second filled with room temperature water at 68 °F (20 °C), and the third filled with very cold ice at 0 °F (-18 °C). Which of these mugs is releasing gaseous water molecules into the dry room air?

All three mugs are releasing gaseous water molecules.

It is a beautiful summer day and the residents of a high-rise apartment building are eating dinner on their balconies. A resident accidentally knocks an empty glass off a balcony that is about 80 meters (260 feet) above the cement patio. The glass would have smashed on that patio after falling for 4 seconds, however, a quick-witted resident catches the glass after it has fallen for only 2 seconds. How far above the patio was the glass when it was caught?

Approximately 60 meters above the patio.

How is a steam engine able to obtain work (ordered energy) from hot steam?

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.

You are at the gym, exercising on a step machine. You have one foot on each of the machine's pedals and you move those pedals up and down as you step. The pedals always push upward on your feet, but they push upward harder on your feet while moving downward than they do while moving upward. When during this exercise is your foot transferring energy to the pedal that it is touching?

As that pedal moves downward.

You are trying to set the world's record for drinking water through the tallest drinking straw. What could you do to have the best chance of setting this record?

Choose a good-weather day when the atmospheric pressure is as large as possible.

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?

Compression of the fuel-air mixture causes its temperature to surge upward so that it ignites.

It's a stormy day, and you're struggling to hold your umbrella steady. The wind is blowing toward the east and your motionless umbrella is pulling your hands upward and eastward. In which direction is the umbrella pushing on the air that passes it?

Downward and westward.

You are flying a kite on a long string and the kite hovers motionless in the sky as the wind blows past it. The kite is high up to your east and you are pulling the kite string downward and westward. In which direction is the kite pushing on the air that passes it?

Downward and westward.

You are trying to set the world's record for drinking water through the tallest drinking straw. You only need to drink one drop of water, so speed doesn't matter. What could you do to have the best chance of setting this record?

Go to the lowest altitude available, preferably sea level or below.

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?

Increase the cable's tension, decrease the cable's mass, or shorten the cable.

Suppose it's a hot summer day, but the air in your room is much colder than the outdoor air. If you remove 1 J of thermal energy from the cold room air and add that 1 J of thermal energy to the hot outdoor air, without doing anything else at all, what happens to the total entropy (disorder) of world?

It decreases.

A juggler tosses a club straight up. Disregarding any effects due to the air, what force or forces are acting on the club while it is above the juggler's hands?

Its weight.

You and your friend carry identical water bottles from the first floor to the fifth floor. You start side-by-side and you finish side-by-side, but one of you uses the stairs while the other climbs straight up a ladder. Which of you did the most work on your water bottle?

Neither. You both do the same work on the water bottle.

A toy top is spinning steadily on a table, with only its sharp point touching the table's surface. What is keeping it spinning?

No torque at all, just its own angular momentum.

You place balls of cookie dough on a shiny metal cookie sheet and pop the sheet into the oven. The oven is being heated by an electric heating element at the bottom of the oven. How does heat flow from the heating element to the cookies?

Primarily by convection of the air.

It's just below freezing outside and your walkway has a layer of slippery ice on it. Which of the following substances will cause that ice to melt if you sprinkle it on the ice?

Salt, sugar, but not sand.

A typical heat pump (an air conditioner run backwards so that it heats the indoor air) consumes 2000 watts of electric power. How much thermal power does it provide to the indoor air?

Significantly more than 2000 watts.

If you're designing an energy efficient automobile, why should you minimize the diameter of the turbulent wake it leaves behind in the air?

Since air in the wake has extracted forward momentum from the car, having less air in the wake means less extracted momentum.

Two children are trying to lift toys using large helium balloons. One child is located in Norfolk, where the altitude is roughly sea level, and the other child is located in Denver, where the altitude is about 5,000 feet above sea level. Their balloons are identical in size and shape, and both locations have the same temperature and weather. Which balloon, if any, can lift more weight?

The Norfolk balloon can lift more weight.

On a windless day, a pitcher throws a baseball toward home plate without any significant spin. After the ball has passed through the air, in which direction is the air moving on average?

The air is moving toward home plate.

You are watching an airshow at the local airport and an acrobatic airplane is flying upside down to impress the crowd. That airplane is traveling forward at a constant horizontal velocity, just 10 feet above the runway! In which direction is the overall force that the airplane exerts on the air?

The airplane is pushing the air directly downward.

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?

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.

You are dragging an old carpet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the carpet is correct?

The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it.

You are moving into a loft apartment and are now dragging an old carpet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the carpet is correct?

The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it.

You are pushing a file cabinet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the file cabinet is correct?

The amount of the force that you're exerting on the file cabinet must be equal to the amount of the force that friction is exerting on it.

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?

The average pressure does not change, but the average density decreases.

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.

The bag's energy changed only a little, but its momentum changed significantly.

You drop an extremely bouncy rubber ball on a cement floor and it rebounds upward almost to its original height. Compare the ball's energy and momentum just before it bounced on the floor with its energy and momentum just after bounced off the floor.

The ball's energy changed only a little, but its momentum changed significantly.

You toss a bottle straight up. Disregarding any effects due to the air, what force or forces are acting on the bottle while it is above your hands?

The bottle's weight.

An automobile engine "knocks" when the gas in its cylinder ignites spontaneously rather than waiting for the sparkplug to ignite it. During which of the 4 strokes can this premature ignition occur?

The compression stroke (when the gas in the cylinder is being compressed).

It's a hot summer day and you turn on the air conditioner to cool your room. As the air conditioner operates, what happens to the energy in the indoor air, the outdoor air, and at the electric company? [Note: the electric company's energy changes when you consume electric power.]

The energies of the indoor air and the electric company decrease, and the energy of the outdoor air increases.

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?

The energies of the indoor air and the electric company decrease, and the energy of the outdoor air increases.

You place three nonflammable objects in a fire. They are identical in shape and size, but one object is black, the second is white, and the third is shiny silver. After a few minutes, all three objects are at the same temperature: 1800 °C. They remain solid and are now glowing with thermal radiation. Which one is glowing most brightly?

The first object (black).

You are rearranging your room and are now sliding your desk across the floor at constant velocity. Which of the following statements about the forces acting on the desk is correct? [Consider only horizontal forces.]

The force that you're exerting on the desk must be equal in amount but opposite in direction to the force that the floor is exerting on it.

You add a teaspoon of salt to a glass of pure water. The salt initially sits at the bottom of the water, but it slowly dissolves so that eventually you have a glass of salt water. Which has more entropy: the glass of pure water with salt sitting at its bottom or the glass of salt water?

The glass of salt water has more entropy.

Suppose a musician is playing a wind instrument (e.g., a flute, clarinet, or oboe) and the density of the air suddenly decreases. There is no change in the air's pressure or in how the musician is playing the instrument. What happens to the instrument's sound?

The instrument's pitch (frequency) increases.

You forgot to tip the bartender who brought a Shirley Temple drink to your luxury hotel suite. So you're leaning out over the balcony of your 20th floor suite and dropping solid gold marbles into the tip jar on the ground floor patio bar. You notice that it takes 4 seconds for each marble to fall into the jar, 20 floors below. When each marble has fallen for only 2 seconds, which floor of the hotel is it nearest? [Note: neglect any effects due to the air.]

The marble is near the 15th floor.

Two guitar strings have the same tension and the same length, but one string is more massive than the other. When you pluck them both simultaneously, how do the fundamental pitches (frequencies) of the two strings compare?

The more massive string has a lower pitch (smaller frequency) than the less massive string.

A mother lifts her toddler upward while that toddler clutches a toy rabbit. Who is doing work on whom?

The mother is doing work on the toddler and the toddler is doing work on the rabbit.

You add sugar to the coffee in your mug and put the lid on. The mug is thermally insulated and sealed, so nothing goes in or out. At first, the mug contains pure coffee and undissolved sugar. Soon, the mug contains sweetened coffee and no undissolved sugar. Compare the entropies (disorders) of these two situations.

The mug of sweetened coffee has more entropy.

You are pulling a wagon full of children up a hill at constant velocity. Which one of the following statements is true?

The net force on the wagon is zero and you are doing work on the wagon.

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?

The object that original appeared black.

You place three nonflammable objects among the red-hot coals of a roaring fire. The objects are identical in shape and size, but one object is black, another is white, and the third is shiny silver. After a few minutes, all three objects are at the same temperature: 1800 °C. They remain solid and are now glowing with thermal radiation. Which one is glowing most brightly?

The object that original appeared black.

Two identical rooms at identical temperatures contain identical collections of atoms. In one room that collection consists of moist air and a small empty cup and in the other room that collection consists of dry air and a small cup of water. Which of the two rooms has the greater entropy (disorder)?

The room containing moist air and an empty bowl has the greater entropy.

Two identical rooms at identical temperatures contain identical collections of atoms. In one room that collection consists of moist air and an empty bowl and in the other room that collection consists of dry air and a bowl full of water. Which of the two rooms has the greater entropy (disorder)?

The room containing moist air and an empty bowl has the greater entropy.

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)?

The room containing the salt water has the greater entropy.

A pitcher throws a spinning baseball toward home plate and the baseball curves toward the pitcher's right. Why did the baseball curve?

The spinning baseball deflected the passing air toward the pitcher's left.

If you pluck a guitar string at different points along its length, it will produce somewhat different sounds. What is different about the string when you pluck it at different points?

The string can vibrate simultaneously in its fundamental and harmonic vibrational modes, and the mixture of those different vibrations depends on where you pluck it.

While decorating your new guitar, you accidently coat one of the guitar strings with spray paint. That paint increases the string's mass. How will that change affect the string?

The string's frequency of vibration (pitch) will decrease.

You're at a lovely outdoor café in New Orleans during the summer and the ice in your glass of water is gradually melting. That glass contained 75% ice and 25% water when it was first poured but now contains 25% ice and 75% water. How has the temperature of the water in that glass changed since it was poured?

The temperature of the water has remained constant.

You're eating lunch outdoors on a hot day and half the ice in your glass of water has melted since you started eating. How has the temperature of the water in your glass changed over that period?

The temperature of the water has remained constant.

A volleyball falls onto the ocean, where it is affected by waves traveling on the ocean's surface. If a steady pattern of wave crests is heading north at 4 mph (4 miles per hour) on a windless day, how will the floating volleyball move as it encounters this wave pattern?

The volleyball will move in a circle, but make no average progress in any direction.

Firefighters are battling a fire on the 10th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the water steadily up to the 8th floor. So they carry the nozzle end of the same fire hose to the top of a 4-story-tall ladder and again point the nozzle upward. How does the speed of the water as it emerges from the nozzle near the top of the ladder compare to its speed when it emerged from the nozzle near the ground?

The water emerging from the nozzle near the top of the ladder travels more slowly.

You are kayaking in Alaska. You reach forward with your paddle, lower the paddle into the water, and then pull the paddle backward. You accelerate forward. What force acts on the paddle to cause you to accelerate forward?

The water exerts a drag force on the paddle, pushing the paddle in the forward direction.

You are paddling a canoe across a lake. You reach forward with your paddle, lower the paddle into the water, and then pull the paddle backward toward you. The paddle, canoe, and you all accelerate forward as you pull the paddle backward. What force causes the paddle, canoe, and you to accelerate forward?

The water exerts a drag force on the paddle, pushing the paddle in the forward direction.

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?

The wings become blunt objects and they stall (they produce large turbulent wakes).

Since a water molecule weighs less than the average air molecule, humid air is less dense than dry air. Suppose that the humidity of the air increases significantly during an orchestra concert. How will the resulting decrease in air density affect the wind instruments (e.g., flutes, clarinets, oboes)?

Their pitches (frequencies of vibration) will increase.

Some satellites orbit the earth at such large distances that they are never in the earth's shadow. These satellites are constantly exposed to full sunlight. With no air around them to take away heat, why don't these satellites continue to grow hotter forever?

Their temperatures rise until they are able to radiate heat away into space as fast as it arrives from the sun.

You are riding a bus that is moving straight ahead at high speed. The bus comes to a curve in the road and begins to turn toward the left. You find yourself pressed against the right side of your seat. What force, if any, is pushing you toward the right?

There is no force pushing you toward the right

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?

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.

You are carrying a child on your back as you walk down a hill. The child is traveling straight at a steady speed. In which direction is the force you are exerting on the child?

Upward (vertical).

The airflow around a dust particle is laminar. What force prevents that dust particle from falling rapidly to the ground and keeps it aloft for a long time?

Viscous drag.

You wake up one very cold winter morning to find the grass outside covered with frost. How did this ice form on the grass?

Water molecules from the moist air landed on the cold grass more frequently than they left the grass, and there was a net accumulation of water molecules as ice.

If you try to cook vegetables with 100 °C air, it takes a very long time. But if you cook those same vegetables with 100 °C steam, they cook very quickly. This is because the steam

condenses on the colder vegetables and releases a large amount of heat to the vegetables.

Water is flowing smoothly through a garden hose that rests on level ground. The hose bends toward the left and the water follows that bend. Neglecting any effects due to the water's viscosity, compare the water just inside the left and right sides of that bend.

Water on the left side has lower pressure and higher speed than water on the right side.

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.]

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.

You are practicing the trapeze at circus camp and you lose your grip on the bar. You fall into the net far below and bounce comfortably up and down. After a few seconds, you settle down at equilibrium in the net. When during your fall and first rebound upward were you accelerating downward?

Whenever you were above your equilibrium in the net.

To avoid tipping over while turning right on a bicycle, why must you lean the bicycle toward your right?

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.

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?

You are causing the column of air inside the pipe to vibrate in its different vibrational modes, each of which has a different pitch.

You are at a tropical resort and your friends have talked you into diving off the top of a cliff into the ocean below. It's a 4-second fall to the ocean. When you have been falling for exactly 2 seconds, you change your mind and instantly grab onto the tree projecting outward from the cliff. Miraculously, you stop safely and hold onto the tree. Your decision to climb up or down now depends on your height on the cliff. Where are you and the tree located on that cliff? [Note: neglect any effects due to the air.]

You are much closer to the top of the cliff than to the ocean below.

A cup of water is in thermal equilibrium. If you stir the water vigorously, the water will become hotter. What causes this rise in temperature?

You do work as you stir the water and that work becomes thermal energy in the turbulent liquid.

Your coffee has cooled off and you decide to heat it the hard way: you stir the coffee vigorously for 10 minutes. The coffee does become slightly hotter. What causes this rise in temperature?

You do work on the coffee as you stir it and viscous effects turn that work into thermal energy.

When you drop a beanbag on cement, the bag doesn't bounce. Suppose you are playing tennis with a beanbag instead of a tennis ball. How should you adjust your tennis racket to make the beanbag travel as fast as possible after you hit it with the racket?

You should loosen the strings so that the racket surface is like a soft trampoline.

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?

Your heavier friend has a period longer than 1 second, your shorter friend has a period of 1 second.

You are walking a dog on a leash when a squirrel runs by. Suddenly, you are all accelerating forward. If the dog is exerting a 50 newton forward force on the leash, the force that the leash is exerting on the dog is

a 50 newton backward force.

The chemical bond that causes two oxygen atoms to cling together as an oxygen molecules is

a deficit of energy—the work needed to separate those two atoms from one another.

A cross-country skier is struggling to get up a hill, so you offer to help. As the skier passes you, you reach out with your hand and exert an uphill force of 80 N (18 pounds) on the skier. When you do this, the skier exerts

a downhill force of 80 N on you.

Two children are balanced on a seesaw, but one child weighs twice as much as the other child. The heavier child is sitting half as far from the pivot as is the lighter child. Since the seesaw is balanced, the heavier child is exerting on the seesaw

a torque that is equal in amount but oppositely directed to the torque the lighter child is exerting.

Wrapping a hot potato in aluminum foil helps keep the potato warm because the shiny aluminum foil is

a very poor emitter of thermal radiation.

Ice cannot be colder than

absolute zero.

To transform 1 kilogram of boiling-hot water at 100 °C into 1 kilogram of steam at 100 °C, you must

add a large amount of heat to the water.

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

air molecules flow out of the envelope's opening and the weight of the air inside the envelope decreases.

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

air pressure at the front of the ball is greater than atmospheric pressure, while the air pressure behind the ball is approximately atmospheric.

When smokejumpers parachute into forest fires, they have with them emergency tents made of shiny aluminum foil. If they're caught in the blaze, they lie flat on the dirt in a low spot with the aluminum tent propped just above them. If the fire passes quickly enough, they have a good chance of surviving it. The tent is made of aluminum because

aluminum reflects most thermal radiation from the fire.

Independent, gaseous water molecules can leave the surface of hot water at 212 °F (100 °C)

and the surfaces of room temperature water at 68 °F (20 °C) and ice at 0 °F (-18 °C).

A skateboarder rides swiftly up the edge of a bowl-shaped surface and leaps into the air. While in the air, the skateboarder flips upside and tosses the skateboard from hand to hand. The skateboarder then rides safely back down the bowl. During the time that the skateboarder and skateboard are not touching anything, one aspect of their motion that is constant is their total (or combined) [note: neglect any effects due to the air]

angular momentum.

A guitar string that normally vibrates with a fundamental frequency of 110 Hz is also capable of vibrating at 330 Hz. When that higher frequency vibration occurs, the string is vibrating

as 3 strings that are each one-third as long as the overall string.

After a volleyball is served and is heading through the air and over the net, it gradually slows down. The primary reason for this slowing is that the air pressure

at the front of the ball is greater than atmospheric pressure, while the pressure behind the ball is approximately atmospheric.

Once a baseball leaves the pitcher's hand and is heading toward home plate, it gradually slows down. The primary reason for this slowing is that the air pressure

at the front of the ball is greater than atmospheric pressure, while the pressure behind the ball is approximately atmospheric.

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

barely moves downward as you push downward on it, so you do almost zero work on it.

A dog and a cat jump horizontally off a wall at the same moment and soon land on the level horizontal field that extends outward from the base of the wall. The dog weighs twice as much as the cat, but the cat was moving forward horizontally twice as fast as the dog when the two animals left the wall. In this situation,

both animals land at approximately the same time, but the cat lands considerably farther from the wall than the dog does.

Two bars of soap slide off of a horizontal counter at the same time, side by side. The green bar of soap weighs twice as much as the orange bar of soap, but the orange bar has twice the velocity of the green bar when the two first lose contact with the counter. In this situation,

both bars hit the floor at approximately the same time, but the orange bar lands considerably farther from the counter than the green bar does.

Two cans of soup, one of which weighs twice as much as the other, roll off of a horizontal table together at the same initial velocity. In this situation,

both cans hit the floor at approximately the same time and at the same distance from the table.

A child is playing on a swing. As long as he doesn't swing too high the time it takes him to complete one full oscillation will be independent of

both the amplitude of the child's motion and of the weight of the child.

A child is playing on a swing. As long as he doesn't swing too high, the time it takes him to complete one full oscillation will be independent of

both the amplitude of the child's motion and of the weight of the child.

You drop a cylindrical can of soup and its flat bottom lands hard on the cement floor. As the result of the liquid-filled can's violent impact with the floor, its sides bulge outward. The bulge(s) is/are located at the

bottom of the can.

During the power stroke in one cylinder of a car's engine, the burned fuel and air push the piston out of the cylinder. In accordance with Newton's third law, the piston pushes back on the burned gas. Overall, the

burned gas does work on the piston and the gas experiences a drop in temperature.

You are designing a chair for a museum. While your chair will be a work of art, it must also be practical and it mustn't tip over easily. To ensure that it stays upright, you design it so that its

center of gravity always rises if you tip it.

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

condenses on the colder vegetables and releases a large amount of heat to the vegetables.

If you blow across the top of a half full bottle of soda you can produce a clear tone. If you take a drink of soda to reduce the amount of liquid in the bottle and try this again the pitch (frequency) of the sound produced will

decrease.

If you blow across the top of a half-full bottle of mineral water you can produce a clear tone. If you take a drink of water to reduce the amount of liquid in the bottle and try this again, the pitch (frequency) of the sound produced will

decrease.

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

decreased and the density inside the bottle has increased.

When water rushing through a fire hose flows around a bend in that hose, its pressure changes. The water pressure

decreases near the inside of the bend and increases near the outside of the bend.

When water flows around a bend in a garden hose, the water pressure

decreases near the inside of the curve and increases near the outside of the curve.

As heat flows from hot soup to a cold kitchen, the entropy (disorder) of the soup

decreases, the entropy of the kitchen increases, and their combined entropy increases.

An air conditioner is cooling the air inside your house on a hot summer day. As a result of the air conditioner's operation, the entropy (disorder) of the indoor air is

decreasing, the entropy of outdoor air is increasing, and the total entropy of both is increasing.

The hotter it is outside, the more electric energy an air conditioner must use to remove each joule of heat from the 72 °F indoor air in your home. It must consume more electric energy on a hotter day because

delivering that joule of heat to the outdoor air creates less entropy as the outdoor air gets hotter.

You are taking a nap on the couch. A foam cushion is supporting your head so that your head is in equilibrium. The cushion is dented downward 2 inches from its equilibrium shape. You lift your head to look at the clock, then let your head drop freely against the cushion. Your head dents the cushion downward 4 inches before rebounding back upward. The point at which your head reaches maximum speed during this drop and bounce is when it is

denting the cushion downward 2 inches.

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

different on different floors, but the sum of pressure potential energy and kinetic energy per liter is the same on different floors.

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

directed toward the center of the track.

To save the earth from an asteroid impact years in the future, engineers land an explosive on the asteroid and blow it to bits. Just before the detonation, the asteroid was heading directly toward mars and just after detonation, the largest piece of asteroid is heading directly toward the sun. Just after the detonation, the total momentum of all the asteroid pieces points

directly toward mars.

A satellite is orbiting the earth in a not-quite-circular orbit. As it moves, the satellite is accelerating

directly toward the center of the earth.

You are riding a tourist train through the hills of northern Italy. The train is currently climbing uphill at constant velocity along a train track that points directly toward a high pass between hills. The force that the train is exerting on you points

directly upward.

You are standing in a cable car that is moving up the side of a mountain at a constant velocity. The force that the cable car is exerting on you points

directly upward.

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

does not flow at all.

The houseware store you have just entered has a uniform temperature throughout. You pick up a heavy copper pot and place it on a soft, fabric mat. As a result of this contact, heat

does not flow at all.

You watch from the ground as a crane lifts a large bucket of cement upward to a construction project. The bucket and cement are moving straight upward at constant velocity. As the crane's cable lifts the bucket, the cable is

doing work on the bucket and the bucket is doing work on the cement it contains.

You are riding a rollercoaster with a loop-the-loop. You have just rolled up the side of the loop and are, at this moment, exactly at the top of the loop. You and the car are upside down, yet you are pressed tightly into your seat. At this moment, you are accelerating

downward at more than the acceleration due to gravity.

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

either the chandelier's weight or the chandelier's amplitude of motion

An automobile's internal combustion engine burns a mixture of fuel and air in its cylinders. It is impossible for this engine to convert all of the chemical potential energy of the fuel and air mixture into mechanical work because burning that mixture increases its

entropy.

An astronaut is orbiting the Earth inside the International Space Station and she is hovering in the middle of the cabin. The net force on that astronaut is

equal to her weight and she is accelerating downward (toward the center of the Earth).

A satellite is orbiting the Earth at an altitude of 100 miles. The net force on that satellite is

equal to its weight and it is accelerating toward the center of the Earth.

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

extract both the egg's kinetic energy and the egg's forward momentum while exerting only small forces on the egg.

To catch a football successfully, you should allow the ball to push your hands in the direction of its travel. Allowing your hands to move with the football is crucial because it allows you to

extract energy from the football.

If you kick a soccer ball straight forward at high speed with no spin at all, the air pressure at its surface will not be uniform. The location of the highest air pressure on the ball's surface will be at its

front (the side farthest from you).

To put a satellite in orbit around the earth, a rocket has two important tasks. First, the rocket must lift the satellite above the Earth's atmosphere. Second, the rocket must

give the satellite such a large horizontal speed that the falling satellite arcs endlessly around the Earth rather than descending to the ground.

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

give the satellite such a large horizontal speed that the falling satellite arcs endlessly around the earth rather than descending to the ground.

If you blow carefully across the top of a drinking straw, it will emit a tone. If you now close off the bottom of the straw with your finger, the tone that it emits will

go down by an octave (its frequency will decrease by a factor of 2).

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

greater than your weight and you are accelerating upward.

When you jump while standing on a bathroom scale, it briefly reads more than your actual weight. During that moment, it's exerting an upward force on you that is

greater than your weight and you are accelerating upward.

A rigid two-blade wind turbine that is experiencing zero net torque

has a constant angular velocity, which may be zero.

You're drinking a cup of hot coffee in an airplane at 35,000 feet. Suddenly the airplane pressurization system fails and the cabin's air pressure decreases abruptly. The coffee begins to boil because its temperature

hasn't changed but bubbles of pure steam are now stable inside it.

If you strike a stiff, spring-like surface with a mallet and listen to the sound it emits, you'll notice that this sound is more complicated than that emitted by a string or a thin bar. That's because surfaces

have overtones that are not integer multiples of their fundamental frequencies.

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

have slowed the water flow through hose and plumbing so that the water wastes less energy doing work against viscous forces.

You are mountain biking through the woods and come to a deep gully. The bottom of the gully is a smooth bowl shape without any obstacles. Neglecting friction and air resistance, you are able to coast down one side and back up the other without pedaling. When you are at the bottom of the gully, you feel

heavier than normal since you are accelerating upward.

Wearing a thin nylon jacket with no additional insulation still helps you stay warm on a cold, windy day. The primary way in which the jacket keeps you warm is by

helping you retain a thin layer of warm air near your skin.

As the water stream from a fountain rises upward in the open air, its gravitational potential energy increases,

its kinetic energy decreases, but its pressure potential energy remains constant.

You are cleaning the siding on your house by spraying water at it from a hose and nozzle. At the center of the stream of water, right where it hits the siding, the water is coming to a complete stop. The pressure in the water at the center of the stream as it touches the siding is

higher than atmospheric pressure.

You are playing with a squirt gun and the narrow stream of water from your toy hits your friend's cheek. At the center of the stream of water, right where it hits his cheek, the water is coming to a complete stop. The pressure in the water at the center of the stream as it touches his cheek is

higher than atmospheric pressure.

Flowing honey is less likely to become turbulent than flowing water because

honey's larger viscosity favors laminar flow.

Ice floats on liquid water because

ice is less dense than water at 0 °C, so the ice experiences an upward buoyant force that is greater than its downward weight.

One warm spring day you and some friends go to the beach at a nearby lake. You are playing with an almost fully inflated beach ball, which has a limp, floppy skin that dents effortlessly when you push on it. Someone accidentally throws the ball it into the ice cold lake. The ball appears to deflate partly on contact with the freezing water, although it has no leak. The large decrease in the ball's temperature caused a large

increase in the density of the air inside the ball.

One warm spring day you and some friends go to the beach at a nearby lake. You are tossing a soft, almost fully inflated beach ball around when someone accidentally knocks it into the lake. Although it is a very hot day, the water is very cold and nobody wants to retrieve the ball. You notice that the ball seems to have deflated somewhat after sitting in the water for a while. The contact with the cool water has caused the temperature of the air inside the ball to drop, resulting in a significant

increase in the density of the air inside the ball.

On a cold morning, you seal your empty plastic water bottle and thus trap the air inside it. Later in the day, the bottle and its contents are much warmer and the elastic sides of the bottle are now stretched outward, so the bottle has slightly more volume than it had in the morning. Since the morning, the air pressure inside the bottle has

increased and the density inside the bottle has decreased.

As air flows around a fast-moving ball, that air has difficulty maintaining laminar flow from the ball's sides to the ball's back. During the air's passage from sides to back, the pressure along each streamline

increases and the airflow slows down.

As air flows around a fast-moving ball, that air has difficulty maintaining laminar flow from the middle of the ball to the back of the ball. During the air's passage from the ball's middle to its back, the pressure along each streamline

increases and the airflow slows down.

At high altitude, a commercial jetliner must compress the outside air before circulating it in the pressurized cabin. But the compressed air must first be sent through an air conditioner because compressing air

increases its temperature.

At high altitude, a commercial jetliner must compress the outside air before circulating it in the pressurized cabin. The compressed air must first be sent through an air conditioner, however, because compressing air

increases its temperature.

At high altitude, a commercial jetliner must compress the outside air before circulating it in the pressurized cabin. But the compressed air must first be sent through an air conditioner because the act of compressing air

increases the air's temperature.

Increasing the amount of carbon dioxide (a greenhouse gas) in the earth's atmosphere

increases the altitude of the earth's effective radiating surface.

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

increases the entropy produced by transferring 1 joule of thermal energy from the flame to the air.

A satellite is traveling around the earth in a circular orbit. It briefly fires its rocket engine to increase its speed in the forward direction; it is suddenly going faster but its direction of travel didn't change. As a result of this speed increase, the orbiting satellite's average distance from the center of the earth

increases.

In a famous ice skating trick, a skater begins spinning with her arms out and then pulls her arms tightly against her body. She is then spinning extremely fast on the tip of one skate. Her angular velocity increases because her angular momentum

is constant but her rotational mass decreases.

You are waterskiing at constant velocity behind a powerful speedboat and your arms and legs are getting tired. The net force acting on you

is zero.

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 barely moves downward as you push downward on it, so you do almost zero work on it

You throw a curve ball that is bending toward your right as it travels away from you. It is able to bend in this manner because

it is deflecting the airflow around it toward your left.

Once water is heated to 100 °C (212 °F) at sea level,

it usually begins to boil, but it requires additional energy to convert from a liquid to a gas without changing temperature.

On a hot, humid day, the liquid perspiration on your wet skin doesn't do a very good job of cooling you off. The weather changes and the air suddenly becomes less humid, although its temperature remains the same. You find that you're cooling off better because water molecules now

land on your wet skin less often, but leave your wet skin at the same rate as before.

On a hot, humid day, the liquid perspiration on your wet skin doesn't do a very good job of cooling you off. If the air were less humid but had the same temperature, you'd cool off better because water molecules would

land on your wet skin less often.

You are standing in a slow-moving stream, facing upstream so that the water is coming toward the front of your body. You are wearing shorts and the water level is slightly above your bare knees. The water experiences perfect laminar flow around each of your nearly cylindrical legs. You measure the water pressure at a specific altitude below your right knee and find that the water pressure is

largest on the front and back of your leg and smallest on the sides of your leg.

A pendulum consists of a metal ball hanging on a cable from a fixed point on the ceiling. To increase the period of that pendulum (the time it takes to complete one full cycle of motion), you should

lengthen the cable.

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

less chemical potential energy than the original wax and oxygen molecules.

When wood burns in air, the water and carbon dioxide molecules that form as the result of combustion reactions have

less chemical potential energy than the original wood and air molecules

Compared to a black iron woodstove, a woodstove made out of shiny gold would be

less effective at heating a room because shiny gold does not radiate heat well.

Your winter jacket contains 8 ounces of goose down insulation, just enough to completely fill the interior of the jacket. Suppose you open the seams and tightly pack 8 more ounces of goose down insulation into the jacket. After sewing up the seams, your jacket will be

less insulating than before, because the excess goose down conducts heat better than the trapped air it replaces.

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,

less ordered energy must become thermal energy to make up for the entropy lost when heat moves against its natural direction of flow.

When an airplane is in level flight at 30,000 feet and moving at constant velocity, the average air pressure just above its wings is

less than atmospheric pressure and the average air pressure just below its wings is more than atmospheric pressure.

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

lower the world's total entropy.

Your luxury apartment has a dining room table that is so enormous, it has a "lazy Susan" in the middle. This large circular platform rotates frictionlessly so that you can "pass" the marmalade jar to your guests by placing that jar on the platform and then rotating the platform. When you replace the empty jar with a full jar from the pantry, the full jar definitely

makes it harder to change the platform's angular velocity.

Your table at a family-style restaurant has a "lazy Susan" in the middle. This large circular platform rotates frictionlessly so that you can "pass" an entree to your friends by placing it on the platform and then rotating the platform. When the server places a new entree on the platform, it

makes it harder to change the platform's angular velocity.

Water hammer occurs when you suddenly stop the flow of water in a pipe. It happens because flowing water has

momentum and can only be stopped by a force.

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

momentum.

Your glass of water has one cube of ice floating at the water's surface. Part of the cube is above the water. When you pour a layer of chilled olive oil onto the water's surface, the ice cube

moves upward slightly.

Your glass of water has one cube of ice floating at the water's surface. Part of the cube is above the water. Olive oil is less dense than water. When you pour a layer of chilled olive oil onto the water's surface, the ice cube

moves upward so that more of the cube is above the water.

You are standing behind a swing, pushing your little cousin on that swing. To make your cousin swing farther and faster, you should only push your cousin forward when your cousin is

moving forward.

You are in the kitchen with three mixing bowls in front of you. One bowl is metal, the second is glass, and the third is plastic. All three are at exactly the same temperature. If you touch the three bowls together,

no heat will flow between the bowls.

You are competing in an archery contest and have just released an arrow toward the target. Neglect any effects due to the air. Once the arrow has left the bow and is heading forward toward the target, it experiences

no horizontal force in the forward direction.

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

no initial steam bubbles form within the liquid water.

You are out for a bicycle ride on a calm, windless day. You are heading northward on a level road and are experiencing a pressure drag force that pushes you toward the south. This air resistance explains why you have to keep pedaling to maintain your constant speed. If someone were to examine the air that you have left behind you after you have passed through it, they would find that the air's average velocity is

northward.

If a golf ball were smooth rather than dimpled, it would

not travel as far after being hit by a golf club.

Near sea level, water normally boils at about 212 °F (100 °C). However, a microwave oven can heat water in a glass container above that temperature if

nothing helps form the initial steam bubbles.

In the game of shuffleboard, you push plastic disks forward and then release them so that they slide across a level playing surface. Once you release a disk, you are no longer pushing and it gradually skids to a stop. Its final position determines your score. As each disk skids to a stop, what becomes of the kinetic energy it had when you released it? That energy is

now thermal energy in the disk and playing surface.

Two puppies are fighting over a toy. Each puppy grips one end of that toy in its mouth and pulls. Suddenly, the puppy on the right pulls especially hard on the toy and moves its end of the toy to the right. The other puppy manages to keep its end of the toy from moving. Alas, the toy breaks and the game ends. Breaking the toy required energy and that energy was provided

only by the puppy on the right.

You are juggling grapefruits in your hands and are about to toss one far above your head. After it leaves your hand, the grapefruit will experience

only the downward force of its weight, both before and after it reaches its peak height.

Flowing pancake syrup is less likely to become turbulent than flowing water because

pancake syrup's larger viscosity favors laminar flow.

The characteristic of a harmonic oscillator that makes it especially suitable for use as a timekeeper in a clock is that its

period of oscillation does not depend on its amplitude (extent of motion).

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

potential energy to increase.

If you blow properly across the top of a soft drink bottle, it will emit a tone similar to that of a flute or a pipe organ. As the tone is sounding, air is oscillating back and forth through the mouth of the bottle. Inside the bottle, the air's

pressure is alternately increasing and decreasing.

You have installed a fountain in your backyard fish pond. Water flows through a pipe to a nozzle, then rises 10 feet upward in the open air. As water flows along a streamline in this system, its energy changes forms several times. As the water passes through the nozzle its energy transforms from

pressure potential energy to kinetic energy and as the water rises to its peak height its energy transforms from kinetic energy to gravitational potential energy.

You are eating at an outdoor restaurant on a cold day and the restaurant has a red hot heating element positioned about 10 feet above you that keeps you surprisingly warm. Heat from that element reaches you

primarily via radiation, with almost no heat flowing to you via conduction or convection.

It's a cold day and you have run out of wood for your fireplace. You place an electric hotplate in the fireplace and turn it on. For safety, you open the chimney flue to let air above the hot plate flow up the chimney and out of the house. The hotplate glows red hot. Heat will flow from the hotplate to people sitting across the room from the fireplace

primarily via radiation, with almost no heat flowing via conduction or convection.

The living room is cold, so your friend brings in an electric hotplate to warm the air. To make sure that no one touches the red-hot surface of that hotplate, your friend places the hotplate on a high ledge near the ceiling. Heat will flow from the hotplate to people sitting near the floor

primarily via radiation, with almost no heat flowing via conduction or convection.

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

primarily via radiation, with almost no heat flowing via conduction or convection.

An air conditioner's compressor takes low density gas and compresses that gas to high density. During this compression process, the gas's

temperature rises and so does its pressure.

When you ride a bicycle, the ground exerts an upward support force on the wheel. When you turn the bicycle, the ground also exerts a horizontal frictional force on the wheel that causes you to accelerate sideways. Leaning the bicycle toward the inside of a turn keeps you from flipping over because the overall force that the ground exerts on the wheel

produces zero torque on you and the bicycle about your combined center of mass.

When you strike a match on the side of the match box, you are using sliding friction to

provide the activation energy needed to initiate the chemical reactions of combustion.

Tightening a guitar string

raises the string's frequency or pitch by stiffening the string's restoring force.

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

reflects infrared light and blocks radiative heat transfer from one pane to the other.

You are standing in the middle of a level subway car that is moving forward at constant velocity when another passenger accidentally spills an enormous container of olive oil. Suddenly, the floor cannot exert any frictional forces on your feet. Because nothing else is touching you, you

remain in the middle of the subway car.

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

remain in the middle of the subway car.

You are practicing tennis alone by hitting a tennis ball forward toward a cement wall. Each time the ball hits the wall, it bounces backward at high speed so that you can hit it again. During its bounce, the ball

retains approximately all of its energy but transfers more forward momentum than it had to the wall.

To win a stuffed animal at the state fair, you simply need to drop a glass marble onto a stationary glass plate and have the marble come to rest on that plate. Unfortunately, when the marble hits the plate, it bounces upward because the marble

retains essentially all of its energy but transfers a large amount of momentum to the plate.

If you place a window air conditioning unit on a table in the middle of your sealed room, plug it in, and turn it on, you will find that the average temperature of your room will

rise.

If you increase the length of the pendulum in your grandfather clock, which previously kept excellent time, you will discover that the clock is

running slow (the clock's minute hand takes more than 60 minutes to complete a full rotation).

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

runs a little slow (causing you to be late for classes).

Your grandfather clock uses a pendulum as its timekeeper. At home, that clock keeps perfect time. When you move the clock to your dorm room, where the earth's gravity is slightly weaker than at home, the clock

runs a little slow (causing you to be late for classes).

If the earth had no atmosphere, the temperature at the earth's surface would be

significantly cooler than it is now.

When a plane is flying through the air at 600 miles per hour, the air entering the inlet duct of its jet engine is traveling

slower than 600 miles per hour and its pressure is higher than atmospheric.

Just mixing gasoline and air together won't make them burst into flames because

something must provide the activation energy needed to initiate the chemical reaction.

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

speed or its density.

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

stay the same and the net force on the balloon would increase slightly in the upward direction.

An airplane cruises at constant velocity into a region of calm, motionless air. After the plane has passed through that region of air, the air's total momentum is

straight downward.

An airplane is cruising horizontally at 30,000 feet and is traveling at constant velocity. The overall force that airplane exerts on the air points

straight downward.

Moments before it's ignited by the sparkplug, the mixture of fuel and air inside an automobile engine cylinder is compressed to very high density. During the compression process, the mixture's

temperature rises dramatically and so does its pressure.

On a humid summer day, perspiration doesn't cool you off much because

the air is almost saturated with water vapor, so there is almost no evaporation.

You're playing tennis on a hot, humid day in August and you are covered with perspiration. Unfortunately, that perspiration doesn't cool you off much because

the air is almost saturated with water vapor, so there is almost no evaporation.

You are filling a large lightweight dry cleaning bag with helium. At first, the plastic bag doesn't float. But as you keep adding helium to the bag, it eventually begins floating because

the average density of the helium-filled bag decreases as it fills and its density eventually becomes less than that of the air it displaces.

You are filling a large plastic bag with helium. At first, the bag doesn't float. But as you keep inflating the bag with helium, it eventually begins floating because

the average density of the helium-filled bag decreases as it fills and its density eventually becomes less than that of the air it displaces.

You are filling a plastic party balloon with helium. At first, the under-filled balloon doesn't float. But as you keep filling it with helium, it eventually begins floating because

the average density of the helium-filled bag decreases as it fills and its density eventually becomes less than that of the air it displaces.

You are a famous stylist, putting the finishing touches on Lady Gaga's hair before her performance. Alas, your bottle of signature hair goo is almost empty! You put the cap on the bottle and swing it rapidly in a circle with its cap end pointing outward. The remaining hair goo collects just inside the cap and you are able to extract enough to complete your work. This technique works because

the bottle's rapid inward acceleration leaves the hair goo behind so that it drifts toward the cap end of the bottle.

Your French fries are getting cold as you wait for your server to bring you a new bottle of ketchup. In frustration, you decide to get the last bits of ketchup out of the old bottle by swinging it rapidly in a circle with the cap-end of the bottle pointing away from you. This technique works because

the bottle's rapid inward acceleration leaves the ketchup behind so that it drifts toward the cap-end of the bottle.

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

the bottle's rapid inward acceleration leaves the shampoo behind so that it moves toward the cap-end of the bottle.

You make a sharp left turn in your car and your cellphone slips off the dashboard and out the right passenger window. The cellphone leaves the car because

the car did not exert enough leftward force on the cellphone to make the cellphone accelerate with the car.

A chandelier hangs motionless from the ceiling. The amount of momentum that chandelier is transferring to the ceiling each second is

the chandelier's weight times 1 second.

You're at the lake and watch two children jump off a dock at the same time. They both kick equally hard during their jumps, but one child jumps mostly upward while the other child jumps mostly forward. After they leave the dock,

the child who jumps forward reaches the water before the child who jumps upward.

A candle is burning in a closed box that is perfectly insulated and isolated from the rest of the world. Because the candle is burning,

the entropy (disorder) of the box and its contents is increasing.

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,

the entropy (disorder) of the room and its contents is increasing.

Although you meant to sign up for "semester abroad," you accidently signed up for "semester aboard." You are now aboard a tiny, perfectly insulated spaceship in deep space. What a mistake! As you play solitaire aboard your tiny ship,

the entropy (disorder) of the ship and its contents is increasing.

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

the fine structure of the goose down traps air and prevents it from undergoing convection.

You are visiting a playground and you notice that a girl on one swing completes each full cycle of motion in much less time than a boy on another swing. The girl has a much shorter period of motion (time between cycles) than the boy because

the girl is riding on a much shorter swing than the boy is riding.

You're at the lake and watch two children jump off a dock. They jump at the same time and at the same speed, but the boy jumps mostly upward while the girl jumps mostly forward. After they leave the dock,

the girl reaches the water before the boy.

A seemingly "haunted" house emits creaking sounds as it cools off at night. Since sound carries energy, the house must obtain that energy from somewhere (other than ghosts and goblins). While this energy begins as thermal energy, the sound doesn't appear until the outside temperature drops well below the temperature of the house because

the house's thermal energy can only become work and sound as heat flows from the hotter house to the colder outside air.

Houses often emit creaking sounds as they cool off at night. Since sound carries energy, the house must obtain that energy from somewhere. While this energy begins as thermal energy, the sound doesn't appear until the outside temperature drops well below the temperature of the house because

the house's thermal energy can only become work and sound as heat flows from the hotter house to the colder outside air.

Two squirrels are fighting over a tasty acorn. Each squirrel is pulling on one side of the acorn and they are not making any progress. At last, the female squirrel holds her side of the acorn motionless as the male squirrel tears his half of the acorn away. Tearing the acorn in half required energy and that energy was provided by

the male squirrel.

When you pull a tablecloth out from under a set of dishes, it's important to pull the cloth as fast as possible because

the momentum transferred to the dishes is proportional to the time during which the cloth pulls on them.

The ocean tides are caused primarily by

the moon's gravity distorting the earth's oceans.

When a cylinder in an automobile's engine is going through the power stroke, the hot burned gas is pushing the piston out of the cylinder. As the piston moves out of the cylinder, the burned gas does work on the piston and

the pressure and temperature of the burned gas both decrease.

You are using a hand-powered pump to add air to a bicycle tire. As you pump air quickly into the tire,

the pressure, density, and temperature of the air in the tire increase.

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

the reduced atmospheric pressure in the mountains allows steam bubbles in the water to grow by evaporation at that lower temperature.

The reason that a watch with a balance ring and a spring keeps good time is that

the ring oscillates back and forth with a constant frequency determined principally by the ring's rotational mass and the spring's stiffness.

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)

the same at all altitudes, but the speed of the spraying water is smaller at higher altitudes.

You take off your shoes to sneak quietly into your home late at night. Unfortunately, it's too dark to see the concrete block your friend left on the floor and your big toe collides with it. The block doesn't move and your foot comes to a complete stop due to the impact. Luckily, you are wearing soft woolen socks because when your foot stops during the impact, your toe transfers

the same momentum, whether or not you are wearing socks, but that transfer takes more time when you are wearing socks.

A builder outsourced the design and construction of a high-rise apartment building, as a result, all 50 floors receive their water from a single pipe. That pipe is fed from a water tank located on the building's roof. On opening day, residents on various floors begin taking showers and have different experiences. They quickly discover that the total energy per liter in the spraying water is (neglecting any effects of viscosity and friction)

the same on all floors, but the speed of the spraying water is smaller on higher floors.

Because of bad planning during the design and construction of a high-rise apartment building, all 50 floors of the building receive their water from a single pipe. That pipe is fed from a water tank located on the building's roof. On opening day, residents on various floors begin taking showers and have different experiences. They quickly discover that the total energy per liter in the spraying water is (neglecting any effects of viscosity and friction)

the same on all floors, but the speed of the spraying water is smaller on higher floors.

You're filming a movie and you arrange for two unoccupied cars to drive horizontally off a tall cliff side-by-side at the same velocity. The Mercedes sedan weighs twice as much as the Mini Cooper. In this situation, the two cars hit the level ground below the cliff at approximately

the same time and at the same distance from the cliff.

A huge abstract iron sculpture has been installed in front of the local art museum. It sits there motionless, "guarding" the main doorway. The sculpture is experiencing two forces: its weight downward and a force upward from the brick courtyard beneath it. We know that these two forces on the sculpture are equal in amount but oppositely directed because

the sculpture is not accelerating, so the two forces must sum to zero.

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

the soup's water molecules have gone directly from solid ice to gaseous water vapor.

You are watching children play a game of tug-o-war with a plastic clothesline. The two teams are pulling at opposite ends of the cord and each team is trying to drag the other team into a mud puddle that lies between them. After a few minutes without progress, the team on the right suddenly pulls hard toward the right. The team on the left has anticipated this threat and is able to keep their end of the rope from moving. The right end of the rope stretches toward the right and the rope breaks. Breaking the rope required energy and that energy was provided by

the team on the right.

Heat flows spontaneously from a warm hot tub to a cool swimming pool because this heat transfer causes

the total entropy of the two objects to increase.

Two toy cars roll off a level table side-by-side at the same time and in the same direction. The cars soon hit the level floor below the table. The cars have identical weights, but the violet car was traveling twice as fast as the yellow car when they left the table. In this situation,

the two cars hit the floor at approximately the same time, but the violet car hits considerably farther from the table than the yellow car.

You and friend are paddling a canoe across a lake. You both reach forward with your paddles raised above the water, lower the paddles into the water, and then pull the paddles backward toward you. The canoe accelerates forward as you pull backward on your paddles, because as you pull backward,

the water pushes forward on your paddles.

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

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.

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

third harmonic mode, as three 1/3rd-length strings.

You are swinging a bucket full of water around you in a big horizontal circle at a constant speed. You are at the center of its circular path. The net force on the bucket points directly

toward you.

You are swinging a can of paint around you in a big horizontal circle at a constant speed. You are at the center of its circular path. The net force on the paint can points directly

toward you.

Compared to an ordinary surface wave on the ocean, a tsunami has a much longer wavelength and therefore

travels much faster and involves water that is much deeper into the ocean.

The first kind of perpetual motion machine provides an inexhaustible supply of mechanical work (or the equivalent of work), but consumes nothing at all from its environment, not even heat. An example would be a black box that consumes nothing yet provides electricity forever. This form of perpetual motion machine is impossible because it

violates the law of conservation of energy.

The second kind of perpetual motion machine provides an inexhaustible supply of mechanical work (or the equivalent of work), but consumes only heat from its constant-temperature environment. An example would be a black box that absorbs heat from the 70 °F room air and converts that heat into electricity forever. This form of perpetual motion machine is impossible because it

violates the law of entropy.

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

viscous drag but not pressure drag.

You are jogging on a hot, humid summer day and are covered with perspiration. Unfortunately, that perspiration doesn't cool you off much because

water molecules are landing from the air onto your perspiration almost as often as they are leaving your perspiration for the air.

Ice cubes gradually shrink in a frost-free freezer because

water molecules go directly from solid ice to gaseous water vapor.

You accidently leave the lid off a container of peach sorbet when you place it in a frost-free freezer. Peach sorbet is sugar, water, and peach juice that have been frozen into tiny particles of peach ice. Six months later, you retrieve the container and find it almost empty because

water molecules have gone directly from solid ice to gaseous water vapor.

When you stand in front of an open refrigerator, trying to decide which flavor of Ben and Jerry's to eat, you feel cold even though no chilled air actually touches your skin. The reason you feel cold is that

you are radiating heat toward the refrigerator but receiving relatively little radiated heat in return.

After clearing the bar in the high jump, you land softly on a giant mattress. Landing on the mattress is much more comfortable than landing on a sand heap of equal size because

you transfer the same momentum to the mattress in coming to a stop as you would have transferred to the sand heap in coming to a stop, but the mattress takes more time to stop you.

Even though your Thanksgiving dinner consists of a tofu turkey, you discover that it contains a wishbone. You and your cousin decide to break the wishbone; the one with the large half gets their wish. Your cousin holds one end of the wishbone motionless as you pull the other end toward you rapidly. The wishbone snaps and you're left holding only a tiny fragment. Better luck next time! Breaking the wishbone required energy and that energy was provided by

you.

You are tossing popcorn straight up and catching it in your mouth. At the moment each piece of popcorn reaches its peak height, its velocity is

zero and its acceleration is downward.

A skateboarder is being pulled up a gradual hill by a bicyclist and they are both moving at constant velocity. The net force on the skateboarder is

zero and the net force on the bicyclist is zero.

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

zero and the net force on the sled is zero.