Physics 105 - Final Exam

Physics 105 - How Things Work - Fall, 2000

Final Examination

Given Monday, December 11, 2000, from 9:00 AM to 12:00 Noon

PART I: MULTIPLE CHOICE QUESTIONS

Please mark the correct answer for each question on the bubble sheet. Fill in the dot completely with #2 pencil. Part I is worth 67% of the grade on this examination.

Problem 1:

Here in Charlottesville, your friend cooks her eggs in boiling water for exactly 3 minutes. But when she visits Denver, with an altitude almost 1 mile higher than here, she has to cook her eggs for more than 3 minutes in boiling water to reach the same consistency. The eggs cook more slowly in Denver because

(A) more of the water's thermal energy is in the form of pressure potential energy.

(B) water boils at a lower temperature at high altitude.

(D) the thermal conductivity of water decreases as the altitude increases.

Problem 2:

You have three incandescent light bulbs that are each consuming 50 W (50 watts) of power. Bulb #1 is a 50W halogen bulb operating at its designed power level. Bulb #2 is a three-way bulb, with 50W, 100W, and 150W settings, which is presently operating at its 50W setting. Bulb #3 is an ordinary 100W light bulb that is connected to a dimmer system so that it is only consuming 50 W. Rank these three bulbs from brightest to dimmest (i.e. put the bulb that that emits the most visible light first).

(A) #2 (brightest), #3 (middle), #1 (dimmest).

(B) #2 (brightest), #1 (middle), #3 (dimmest).

(D) #1 (brightest), #2 (middle), #3 (dimmest).

Problem 3:

When you casually toss a melon into the hanging basket of spring scale at the grocery store, the basket bounces up and down a couple of times. If you now toss a second melon into that basket, along with the first melon, the basket will begin to bounce again. This time the frequency of that bouncing will

(A) be the same rate as when it contained just one melon.

(B) be slower than when it contained just one melon.

(D) depend on whether the second melon was heavier or lighter than the first melon.

Problem 4:

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: the 68 °F (20 °C) temperature of the room. If you touch the three bowls together,

(A) heat will flow from the plastic bowl to the glass bowl, and from the glass bowl to the metal bowl.

(B) heat will flow from the metal bowl to the glass bowl, and from the glass bowl to the plastic bowl.

(D) heat will flow from the glass bowl to both the plastic bowl and the metal bowl.

Problem 5:

An ordinary incandescent light bulb contains some inert gas inside its glass enclosure because the gas increases

(A) the filament's life while causing a small decrease in the bulb's energy efficiency.

(B) the bulb's energy efficiency while causing a small decrease in the filament's life.

(D) both the filament's life and the bulb's energy efficiency.

Problem 6:

You accidentally bump into a bookcase. It tilts briefly but then returns to upright, and you breathe a sigh of relief. When you first bumped the bookcase, its center of gravity moved

(A) upward and its gravitational potential energy increased.

(B) downward and its gravitational potential energy decreased.

(D) upward and its gravitational potential energy decreased.

Problem 7:

A wave travels across the water on a lake, heading northward. As the result of this wave's passage, water on the surface of the lake

(A) moves toward the north by a distance that is proportional to the amplitude (height) of the wave.

(B) returns to its original location and makes no overall movement.

(D) moves toward the north by a distance equal to one wavelength of the wave.

Problem 8:

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) viscous drag but no pressure drag.

(B) neither viscous drag nor pressure drag.

(D) both viscous drag and pressure drag.

Problem 9:

The brass pendulum of a particular grandfather clock has a mass of 2 kilograms and completes its swing once every 2 seconds. If you were to replace the brass pendulum with an identically shaped gold pendulum having a mass of 4 kilograms, it would complete its swing once every

(A) 4 seconds.

(B) 2 seconds.

(D) 8 seconds.

Problem 10:

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

(A) the cold refrigerator is radiating cold toward you and is lowering the temperature of your skin directly.

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

(D) you can sense the presence of nearby cold air, even though it is not exchanging cold with your skin.

Problem 11:

A stunt pilot flips her plane upside-down and flies horizontally past the spectators. While her plane and its wings are upside-down and she is flying horizontally, the average air pressure is highest on the

(A) sky side of each wing and the average air speed is highest on the ground side of each wing.

(B) sky side of each wing and the average air speed is highest on the sky side of each wing.

(D) ground side of each wing and the average air speed is highest on the sky side of each wing.

Problem 12:

You're taking a nap on the couch. A pillow is supporting your head so that your head is in equilibrium. The pillow is dented downward 2 inches from its equilibrium shape. Someone walks into your room so you lift your head off the pillow. You then let your head fall freely against the pillow. Your head bounces off the pillow, denting the pillow downward 4 inches before rebounding back upward. The point at which your head reaches maximum speed during this fall and bounce is when it is

(A) just touching the pillow as it rebounds back upward.

(B) denting the pillow downward 2 inches as it travels downward.

(D) just touching the pillow as it travels downward.

Problem 13:

You open the refrigerator in your room and put in a case of room-temperature root beer. After an hour, the root beer is ice cold. If your room air didn't exchange any heat with the outdoor air during that time, the room air will be

(A) colder because the refrigerator reverses natural heating, so that things get colder rather than hotter.

(B) colder because as the refrigerator struggles to cool the root beer, some of the cold it produces inevitably leaks out into the room as the result of imperfect insulation.

(D) warmer because some of the heat from the root beer inevitably leaks out into the room as the result of imperfect insulation.

Problem 14:

A harmonic oscillator has energy as it vibrates. While complicated harmonic oscillators can involve many different forms of energy, the fewest energy forms that a vibrating harmonic oscillator can have is

(A) one.

(B) three.

(D) zero.

Problem 15:

Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun rises near the seashore.

(A) The surface wind will blow from the land toward the water.

(B) The surface wind will blow alternately back and forth along the shore, parallel to the boundary between land and water. It will reverse directions every few minutes.

(C) The surface wind will blow steadily in one direction along the shore, parallel to the boundary between land and water.

(D) The surface wind will blow from the water toward the land.

Problem 16:

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

(A) honey's large density favors laminar flow.

(B) water's large viscosity favors turbulent flow.

(D) honey's large viscosity favors laminar flow.

Problem 17:

When the space shuttle is in orbit outside the atmosphere, its orientation becomes completely flexible. In which orientation do the astronauts experience the greatest sensation of weightlessness?

(A) When the tail of the shuttle is pointing in the direction of its velocity.

(B) When the shuttle is turned at right angles to the direction of its velocity.

(D) When the nose of the shuttle is pointing in the direction of its velocity.

Problem 18:

A sealed bottle contains only liquid water and gaseous water. The container's temperature can be

(A) below 100 °C only.

(B) above 100 °C only.

(D) below 100 °C, equal to 100 °C, or above 100 °C.

Problem 19:

If you place one end of a copper bar in the fire and hold on to the other end, you're likely to have hot fingers very soon. The main carrier of thermal energy as heat flows through that metal bar is/are

(A) vibrating atoms pushing against one another.

(B) molecules moving through the bar.

(D) electrons moving through the bar.

Problem 20:

You are trying to clean your car and have just poured a bucket of water across the hood. The dirt on the surface barely moved at all as the water flowed past it. That's because

(A) the moving water has zero kinetic energy, due to Bernoulli's equation.

(B) the moving water has zero pressure, due to Bernoulli's equation.

(D) water exerts no significant drag forces on very small particles.

Problem 21:

Which of the following quantities is not conserved?

(A) energy

(B) angular momentum

(D) momentum

Problem 22:

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 work done on the dishes by the cloth is proportional to the time during which the cloth pulls on them.

(B) the weight of the dishes on the cloth is proportional to the time during which the cloth is moving.

(C) the force of sliding friction that the cloth exerts on the dishes is proportional to the time during which the cloth is moving.

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

Problem 23:

To make it less likely that a car engine will "knock" (have its fuel/air mixture ignite too early), the engine is designed so that

(A) the fuel/air mixture is not compressed too tightly.

(B) the fuel/air mixture is compressed as tightly as possible.

(D) the fuel/air mixture stays at atmospheric pressure until the sparkplug fires.

Problem 24:

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?

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

(B) They have solar panels that convert the sun's thermal radiation completely into electricity and avoid any need to eliminate heat.

(D) Because they are isolated from the sun by empty space, the sun's heat can't reach them and they don't experience any changes in temperature.

Problem 25:

One of the strength training machines in the exercise facility has an interesting behavior: as you lift its handles upward, you must push up with a force of 450 newtons (100 pounds). But as you lower its handles back downward, you must push up with a force of 600 newtons (133 pounds). During your exercise routine, you move these handles slowly up and down a dozen times, and leave them exactly where you found them. As the result of this routine, your total energy (the total energy of you personally, and not including that of the machine)

(A) decreases.

(B) stays the same but you convert thermal energy into food energy.

(D) stays the same but you convert food energy into thermal energy.

Problem 26:

The space shuttle is orbiting the earth at an altitude of several hundred kilometers and completes each circular orbit in about 90 minutes. If the pilot fires the rocket engines for a few minutes, increasing the shuttle's speed in the forward direction, it will

(A) shift into a new circular orbit with a larger diameter but will still complete each orbit in about 90 minutes.

(B) shift into a new elliptical orbit that is larger than its previous circular orbit and will complete each orbit slower--in more than 90 minutes.

(D) remain in the same circular orbit but will complete each orbit faster--in less than 90 minutes.

Problem 27:

Which of these stars has the hottest surface temperature?

(A) A yellowish star.

(B) A reddish star.

(D) A bluish star.

Problem 28:

A car has been wrapped in thermal insulation so that it can't lose any heat to the surrounding air. As a result of this insulation, the car's engine will

(A) lose its ability to turn thermal energy into work.

(B) become more fuel-efficient because it will retain more of the burned fuel's energy.

(D) be essentially unaffected, since its main function--producing ordered work--is not dependent on disordered heat.

Problem 29:

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

(A) you transfer less momentum to the mattress in coming to a stop than you would have transferred to the sand heap in coming to a stop.

(B) you transfer more momentum to the mattress in coming to a stop than you would have transferred to the sand heap in coming to a stop.

(C) the force that the mattress exerts on you to stop your descent is much less than the force that the sand heap would have exerted on you.

(D) your velocity is less as you land on the mattress than it would have been if you'd landed on the sand heap.

Problem 30:

The tides are strongest near the equator because that's where the

(A) centripetal force of the earth is strongest.

(B) earth's gravity is weakest.

(D) tidal bulges caused by the moon are tallest.

Problem 31:

A stream of smoothly flowing water arcs through the air and hits the side window of a house. It then spreads out smoothly in all directions along the window. At the surface of the window, right where the stream of water hits it, the water's pressure is

(A) lower than atmospheric and the water's speed is faster than in the stream.

(B) higher than atmospheric and the water's speed is faster than in the stream.

(D) lower than atmospheric and the water's speed is slower than in the stream.

Problem 32:

Mike and Johnny are in trouble for scuffling in the school cafeteria. While Mike admits that he pushed Johnny, who immediately fell over backward, Mike claims that Johnny pushed back and is thus just as guilty. From the perspective of physics,

(A) Johnny didn't push back on Mike.

(B) Johnny did push back on Mike, with exactly the same amount of force.

(D) Johnny pushed back on Mike, but with more force than Mike exerted on him.

Problem 33:

Two steel balls, one of which weighs twice as much as the other, roll off of a horizontal table with the same speeds. In this situation,

(A) both balls impact the floor at approximately the same horizontal distance from the base of the table.

(B) the lighter ball impacts the floor at about half the horizontal distance from the base of the table than does the heavier.

(C) the heavier ball impacts the floor at about half the horizontal distance from the base of the table than does the lighter.

(D) the heavier ball hits considerably closer to the base of the table than the lighter, but not necessarily half the horizontal distance.

Problem 34:

You're sitting on a park bench while your dog walks at the end of a spring-loaded leash. This leash emerges from a plastic container with a handle and can extend up to 5 meters (17 feet) if the dog pulls on it hard enough. As the leash extends outward, a spring in the container stretches. When the dog stops pulling, that spring then retracts the leash back into the container. As the dog pulls the leash outward, stretching the spring, she does work on the leash. During which meter of extension does the dog do the most work on the leash?

(A) The work the dog does is the same during each of the five meters of extension.

(B) During the first meter--when the leash first begins to extend.

(D) During the third meter--when the leash is at the middle of its extension.

Problem 35:

If you hold the bottom of a water-filled test tube and heat the top of that tube with a flame, the water inside will boil while your fingers remain cool. If you reverse this arrangement--holding the top of the tube and heating the bottom of the tube--you'll burn your fingers. The reason for this difference is that

(A) heat flows naturally from a hot object to a cold object, not the reverse.

(B) conduction doesn't function when the hot object is above the cold object.

(D) radiation doesn't function when the hot object is above the cold object.

Problem 36:

Ice floats in your glass of water because

(A) the 2nd law of thermodynamics prevents a solid from sinking in its own liquid form.

(B) having ice sink in liquid water would decrease the overall entropy of the system.

(D) the density of ice is less than the density of water.

Problem 37:

You are in a dark 20 °C room, looking at a perfectly shiny metal ball that has a temperature of 1000 °C. The ball doesn't emit any visible light because the shiny ball

(A) isn't hot enough to emit visible light.

(B) neither emits nor absorbs any thermal radiation.

(D) has none of the flat surfaces needed to emit light.

Problem 38:

When a basketball bounces against the ground and dents, the air inside that ball is temporarily compressed. The compression ends when the ball undents during the rebound. The temperature of air inside the ball

(A) remains constant throughout the bounce, because thermal energy is conserved.

(B) decreases during the denting process and increases during the undenting processes.

(D) increases during both the denting and undenting processes.

Problem 39:

You fill two identical mugs with coffee, but the coffee in one mug is hotter than that in the other mug. You place the two mugs simultaneously in a microwave oven and turn it on briefly. As a result, you add 1 joule of thermal energy to each mug. Which mug experiences the larger increase in entropy (if any)?

(A) The two mugs experience equal increases in entropy.

(B) The mug containing the colder coffee experiences the larger increase in entropy.

(D) The mug containing the hotter coffee experiences the larger increase in entropy.

Problem 40:

It's a windy day and there are waves on the surface of the open ocean. The wave crests are 40 feet apart and 5 feet above the troughs as they pass a school of fish. The waves push on fish and making them accelerate. The fish don't like this jostling, so to avoid it almost completely the fish should swim

(A) as fast as possible.

(B) at least 20 feet below the surface of the water.

(D) as close to the surface of the water as possible.

Problem 41:

Many old homes were heated by steam. The steam was produced in a basement boiler and it floated upward through pipes to radiators in various rooms. The steam became water inside those radiators and sank downward through the pipes to the boiler to begin its journey again. In the process, the radiators heated the room air. The rising steam and the descending water both had exactly the same temperature, so where did the thermal energy that heated the room air come from?

(A) From the work done when steam contracted to become liquid water.

(B) From the gravitational potential energy released when the dense water descended.

(D) From the kinetic energy of the fast-flowing steam as it turned into slow-flowing liquid water.

Problem 42:

You are bouncing up and down on a springboard, preparing to dive into the pool. While you're in the air above the board, your acceleration is

(A) zero because you are not touching anything.

(B) upward and constant until you reach the peak, then it becomes downward and constant.

(C) initially upward but it gradually diminishes to zero as you reach the peak and then it gradually becomes more and more downward.

(D) downward and constant.

Problem 43:

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

(A) cannot experience nonuniform accelerations (accelerations that vary from place to place).

(B) have overtones that aren't integer multiples of their fundamental frequencies.

(D) are harmonic oscillators.

Problem 44:

Which of the following produces the most disorder (entropy) when done in the most efficient possible manner?

(A) Stretching a 10-kilogram spring 10 meters, using energy from water flowing in a river.

(B) Lifting 1000 kilograms of water upward a distance of 6 meters, using energy from a windmill (a huge wind-driven fan).

(D) Raising a 7-kilogram bowling ball 1000 meters into the sky, using energy from a car battery.

Problem 45:

You are holding a drinking straw in your hand so that both its ends are open to the air. When you blow air across one of those ends, the air in that straw vibrates and the straw emits a tone--its fundamental pitch. If you replace the air in the straw with carbon dioxide, which is more dense than air, the sound that the straw emits will

(A) have the same pitch but will decrease in volume.

(B) decrease in pitch (shift to a lower frequency).

(D) have the same pitch but will increase in volume.

Problem 46:

The air in this room consists of countless tiny, independent molecules. You can be sure that these air molecules won't all shift spontaneously to the other side of the room (leaving you in a vacuum) because that would

(A) violate Newton's laws of motion.

(B) be extremely unlikely and therefore violate the 2nd law of thermodynamics.

(D) not conserve energy and therefore violate the 1st law of thermodynamics.

Problem 47:

At what place in or near the jet engine is gas moving the fastest relative to the flying airplane?

(A) In the air flowing into the engine's inlet duct.

(B) In the plume of exhaust gas flowing out of the engine's outlet duct.

(D) In the engine's compressor section.

Problem 48:

The maximum speed a rocket can achieve is

(A) the speed of light.

(B) equal to the speed of its exhaust plume.

(D) greater than the speed of its exhaust plume but less than the speed of light.

Problem 49:

A fine crystal wineglass (actually made from lead-based glass) emits a long, pure tone when you flick it with your finger, while a cheap ordinary wineglass emits a "thunk" sound instead. Although you can break either wineglass with sound by choosing the right tone and making it sufficiently loud, it's easier to break the crystal wineglass because the crystal wineglass

(A) is made from a weaker material and fractures more easily.

(B) vibrates in response to a broader range of pitches.

(D) can't bend at all without breaking.

Problem 50:

An incandescent light bulb places its tungsten filament inside a glass enclosure because the enclosure

(A) allows the pressure around the filament to be reduced so that the tungsten doesn't melt.

(B) keeps the tungsten atoms from subliming.

(D) keeps the filament from losing heat to its surroundings.

PART II: SHORT ANSWER QUESTIONS

Please give a brief answer in the space provided. Words written outside of the allotted space will not be read during grading. Part II is worth 33% of the grade on this examination.

Problem 1:

Pine derby cars are small wooden cars that roll down a gently curving track that starts with a fairly steep slope and gradually becomes less steep. The track ends up traveling horizontally for several meters before the finish line. The cars are released from rest and the first one that crosses the finish line at the end of the track wins.

(A) Assuming no air resistance or friction, during which part of its trip does the car have its greatest speed?

(B) Assuming no air resistance or friction, during which part of its trip does the car have its greatest acceleration?

(C) In reality, friction does affect these little cars. The plastic car wheels spin on fine, stationary wire axles. There is friction between each wheel and the ground, and there is friction between each wheel and the axle that supports it. Why is more energy wasted by friction between the wheel and axle than by friction between the wheel and ground?

(D) You must put a 20-gram weight on your car to reach the required racing weight. If you want your car to travel as fast as possible, roughly where on the car should you put that weight? (This is a challenging question that I have been asked dozens of times by the parents of children with pine derby cars. If you think in terms of energy, you should be able to answer this question.)

Problem 2:

Since firefighter use water to put out fires, handling that water is half their job. That job becomes particularly difficult when they are fighting a fire in a high-rise building.

(A) The water pressure in a fire hydrant is about 500,000 pascals above atmospheric pressure (about 5 times atmospheric pressure plus ordinary atmospheric pressure). When the firefighters attached a hose directly to a fire hydrant, they find that water won't flow out of the hose above the 10th floor of the building, located about 50 meters above the sidewalk. Why won't the water flow?

(B) A spectator suggests that the firefighters return to the 8th floor, where water does flow from the hose, and attempt to spray water up the stairwell to the 11th floor. Explain why this strategy will or will not work.

(C) The firefighters find that water leaving a hose with a narrow nozzle on it travels faster than water leaving that same hose with no nozzle. Why does narrowing the opening of the hose speed up the water emerging from it

(D) When water hits hot material in a fire, it turns to steam. This steam takes up much more space than the water did and displaces air from the room. Without oxygen to sustain it, the fire quickly goes out. But the hot material must be much, much hotter than 100 °C, water's boiling temperature, for the water that hits it to turn completely into steam. Why?

Problem 3:

You and a friend are playing pool (billiards) at a bar one evening. In this game, one ball (the cue ball) is used to knock the other balls into pockets around the edges of a table. For this problem assume that there is no friction between the balls and the table.

(A) It is your shot and you hit the cue ball toward one of the other balls. If the two balls have the same mass and the cue ball hits the other ball squarely, the cue ball will stop and the other ball will begin to move. What will the velocity (magnitude and direction) of the other ball be after the collision? (Answer by comparing to the original velocity of the cue ball.)

(B) If the cue ball had twice the mass of the other ball, would the cue ball remain stopped after the collision?

(C) If the cue ball had half the mass of the other ball, which ball would experience a greater force during the collision?

(D) If the cue ball strikes one of the table's side bumper at right angles, it will rebound directly backward; the ball's velocity will reverse perfectly. Will the ball's (1) energy and (2) momentum change as the result of this bounce, and if so, by how much?

Problem 4:

Because of the greenhouse effect, it's important to reduce our consumption of fossil fuels. With that in mind, scientists and engineers at Ideal Motors Corporation are designing a car that will use as little gasoline as possible.

(A) Their first prototype moves without any sliding friction at all, inside or out, so when it travels along a horizontal roadway, the only horizontal force it experiences is air resistance (pressure drag). The force that air resistance exerts on the car increases as the car's speed through the air increases, but a faster-moving car gets to its destination faster. If you are trying to minimize the fuel needed to travel 100 km along a horizontal road at constant velocity, how fast should you drive this car or does it not matter?

(B) Their second prototype is so well built and aerodynamically perfect that it moves without either air resistance or sliding friction. It can coast at constant velocity along a horizontal roadway for hours on end, even with the engine turned off. What force, if any, pushes the car forward while it is coasting like this?

(C) To get the second prototype moving, the engine must twist the car's wheels so that the ground pushes the car forward. The more passengers the car contains, the harder and/or longer the ground must push forward on the car to get it up to highway speed. Why do the occupants of the car affect the starting process in this manner?

(D) The second prototype has reached highway speed and is traveling at constant velocity along the horizontal road. How does the number of passengers in the car affect the amount of energy the engine must supply during the 100 km trip at constant velocity?

Problem 5:

Prairie dogs are cute little burrowing animals that live in the Midwest and are wonderful or a nuisance, depending on whether you own the land they dig up. What makes them interesting to physicists is that they use aerodynamics to ventilate their underground homes.

(A) A prairie dog digs a long, nearly horizontal tube underground and opens each end of the tube to the surface. If both openings were identical--simply level holes cut in the flat, horizontal ground above tube--air wouldn't naturally flow through the tube, even when the wind was blowing overhead. Why not?

(B) However, the prairie dog builds a raised mound or "dome" around one of the tube ends. The tube opening is placed at the highest point of the dome, far above the dome's base and the level ground around the dome. As wind blows across the level ground, it encounters the dome and deflects. The first deflection occurs when the air bends upward as it collides with the base of the dome. This air deflects outward--away from the dome's surface. Compare the speed and pressure of the air near base of the dome to their values in the open air stream. (Just indicate more, less, or equal for each quantity.)

(C) The second deflection occurs when the air bends downward as it arcs around the top of the dome. This air deflects inward--toward the dome's surface. Compare the speed and pressure of the air near the top of the dome to their values in the open air stream. (Just indicate more, less, or equal for each quantity.)

(D) Since one end of the prairie dog's tube opens at the top of the dome and the other opens onto level ground, air flows through the tube from one end of the tube to the other whenever the wind blows. Toward which end of the tube does the air flow (dome end or flat end), and what pushes the air in that direction?

Problem 6:

You're in a festive mood, so you decide to light candles for your dinner party.

(A) You strike a match by rubbing it across the side of the matchbox. Why does this action cause the match to ignite?

(B) Liquid wax doesn't burn but gaseous wax does. In terms of individual wax molecules, how does raising the temperature of the liquid wax increase the density of gaseous wax nearby?

(C) Which molecules are "more tightly bound" (require more energy to separate): (1) the wax and oxygen molecules before burning or (2) the water and carbon dioxide molecules they become after burning?

(D) When you blow out the candle, a white mist rises from the wick for a few seconds. What is that white mist?