Physics 105 - How Things Work - Fall, 2002

Final Examination

Given Wednesday, December 11, from 9:00 AM to 12:00 PM

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 the final examination.

Problem 1:

The temperature of a glass of ice water (a mixture of ice and water)
(A) is proportional to the ratio of water to ice.
(B) depends on the total volume of ice and water in the glass.
(C) is 0 °C.
(D) is proportional to the ratio of ice to water.

Problem 2:

You live in a cylindrical high-rise apartment building. It looks like a giant upright can with windows. Your apartment has a window on the south side of the building and you have noticed that the air pressure outside that window varies according to the direction of the wind. That pressure affects airflow into or out of your window. When the wind blows from west to east, the air pressure outside your window is
(A) above atmospheric pressure and air flows out of your window.
(B) above atmospheric pressure and air flows into your window.
(C) below atmospheric pressure and air flows out of your window.
(D) below atmospheric pressure and air flows into your window.

Problem 3:

The frequencies of the modes of vibration in a single violin string are related to one another. If the string's fundamental frequency is 440 Hz (440 cycles-per-second), then the next 3 consecutive frequencies are
(A) 550 Hz, 660 Hz, and 770 Hz.
(B) 880 Hz, 1320 Hz, and 1760 Hz.
(C) 660 Hz, 880 Hz, and 1100 Hz.
(D) 880 Hz, 1760 Hz, and 3520 Hz.

Problem 4:

Burning fuel in an engine turns the ordered chemical potential energy in gasoline into disordered thermal energy in the hot burned gases. The engine's ability to extract some work from this thermal energy reflects the fact that
(A) there is remaining order in an unequal distribution of temperatures: a hot region and a cold region.
(B) about 25% of thermal energy is actually ordered and can be extracted as work.
(C) about 10% of thermal energy is actually ordered and can be extracted as work.
(D) the second law of thermodynamics is only a statistical law and doesn't always hold true.

Problem 5:

Which of the following will encourage ice to melt into water (by making liquid water more stable relative to solid ice)?
(A) salt, sugar, but not sand.
(B) salt, sugar, and sand.
(C) salt, but not sugar or sand.
(D) salt, sand, but not sugar.

Problem 6:

Two jet engines obtain the same amount of thrust by pushing air backward. One engine, a turbojet, pushes a small amount of air backward at very high speed. The other engine, a turbofan, pushes a large amount of air back at a slower speed. Both engines transfer the same amount of backward momentum each second to the air they push on. During this process, the energy they transfer to the air is
(A) greater for the turbofan than for the turbojet.
(B) zero for both jet engines.
(C) greater for the turbojet than for the turbofan.
(D) equal for both jet engines, but more than zero.

Problem 7:

When a log is floating on water, much of the log is above the water and is actually surrounded by air. If that surrounding air were to suddenly be replaced by an oil that is less dense than the log, the log would
(A) float at the same height as before the air left.
(B) move upward slightly and float somewhat higher (less deep) in the water.
(C) sink to the bottom of the water.
(D) move downward slightly and float somewhat lower (deeper) in the water.

Problem 8:

A steady, horizontal stream of water from a hose strikes a wall. As the water hits the wall, its velocity is forward, its acceleration is
(A) forward, and its pressure is increasing.
(B) backward, and its pressure is increasing.
(C) backward, and its pressure is decreasing.
(D) forward, and its pressure is decreasing.

Problem 9:

A piece of driftwood floats on the sea in the passing waves. There is no wind and the sea has no current. When the wood is exactly on the top of a wave crest, the wood's velocity is
(A) zero (the wood is not moving).
(B) horizontal and points in the wave's direction of travel.
(C) vertical.
(D) horizontal and points opposite to the wave's direction of travel.

Problem 10:

A springboard diver leaps upward from the springboard, rises dramatically to a peak height, and than drops impressively into the water below the board. Neglect any influences of air or the atmosphere. During this trip, the diver experiences
(A) an upward net force that gradually diminishes to zero at the peak height and then becomes a downward net force.
(B) a constant upward net force on the way up and a constant downward net force on the way down.
(C) a downward net force that is proportional to the diver's height above the water.
(D) a constant downward net force.

Problem 11:

You are flying a kite in a steady, horizontal breeze and the kite is maintaining a steady position in the sky. After it passes the kite, the air in the breeze
(A) has separated into two streams, with the top stream deflected upward and the bottom stream deflected downward.
(B) is still moving horizontally.
(C) has been deflected upward somewhat.
(D) has been deflected downward somewhat.

Problem 12:

A single pipe delivers water to all 4 floors of a house. Compared to water flowing to the basement bathroom, water flowing to the attic bathroom has
(A) less total energy per liter, but the same pressure.
(B) the same total energy per liter, but less pressure.
(C) less total energy per liter and less pressure.
(D) the same total energy per liter and the same pressure.

Problem 13:

A stream of water travels essentially horizontally through the air from a nozzle to a flower. While it is traveling freely through the air, this stream of water experiences
(A) a constant forward horizontal force.
(B) a forward horizontal force that diminishes in proportion to the distance from the nozzle.
(C) a forward horizontal force that increases steadily to the midpoint of the flight and then decreases steadily to zero at the flower.
(D) zero forward horizontal force.

Problem 14:

The strings of an acoustic guitar are each attached at one end to a flexible surface so that the surface can move as a string vibrates. This arrangement is crucial to the volume of the guitar because
(A) a rigid surface would keep the string from vibrating.
(B) the surface does work on the vibrating string, adding energy to the string and increasing the string's volume.
(C) the vibrating string does work on the surface and that surface does work on the air to create sound.
(D) a flexible surface prolongs the string vibration time so that each tone lasts longer.

Problem 15:

Airports often provide you with moving sidewalks to help you get from one place to another quickly and easily. Suppose you are riding one of these sidewalks up a gentle hill to your departure gate. You are traveling at a constant velocity, forward and slightly upward. Neglect any air resistance. During this time, the sidewalk is pushing you
(A) in the direction you are moving (up the hill) and you are doing work on the sidewalk.
(B) upward and forward, but it is not doing any work on you.
(C) in the direction you are moving (up the hill) and it is doing work on you.
(D) straight up and it is doing work on you.

Problem 16:

Steam at 100 °C is much more effective for cooking broccoli than air at 100 °C because steam
(A) undergoes convection much better than does air.
(B) at 100 °C water is much hotter than air at 100 °C.
(C) is an electric conductor and thus a much better conductor of heat than is air.
(D) condenses to water on the broccoli and releases chemical potential energy.

Problem 17:

You have an indoor swimming pool in one room of your 87-room mansion. The ventilation is turned off in that room and the air and water are at the same temperature. You observe that the amount of water in the pool remains precisely constant—water is neither evaporating nor condensing. If you were to examine the water's surface microscopically to see if any water molecules were landing on the water's surface or leaving that surface, you would find that
(A) both landing and leaving are occurring, but that landing takes place more often than leaving.
(B) both landing and leaving are occurring, but at exactly equal rates.
(C) both landing and leaving are occurring, but that leaving takes place more often than landing.
(D) both landing and leaving are absent—no molecules are landing or leaving the water.

Problem 18:

A bicycle automatically steers so as to return you to an unstable equilibrium. That unstable equilibrium occurs when your center of gravity is
(A) at its maximum possible height.
(B) behind the rear wheel.
(C) at its minimum possible height.
(D) in front of the front wheel.

Problem 19:

To accelerate to the left, an airplane
(A) pivots horizontally so that is nose is to the left of its tail.
(B) tips so that its right wing is lower than its left wing.
(C) tips so that its left wing is lower than its right wing.
(D) pivots horizontally so that its nose is to the right of its tail.

Problem 20:

A flutist in the symphony drank too much root beer before the concert and burps noiselessly during his flute solo. The carbon dioxide gas in his stomach emerges from his mouth and fills the flute. Carbon dioxide gas is denser than air. As a result of this change in the flute, the flute's
(A) volume becomes softer than normal, but its pitch stays the same.
(B) pitch becomes lower than normal but its volume stays the same.
(C) volume becomes louder than normal, but its pitch stays the same.
(D) pitch becomes higher than normal, but its volume stays the same.

Problem 21:

The upright bar of a football goalpost is basically a spring. If you bend it, it experiences a restoring force that is proportional to its displacement from equilibrium. During a football game, the ball hits the upright bar and bends it 1 foot away from equilibrium. The bar vibrates back and forth with a period of 1 second. If the football had bent the bar 2 feet away from equilibrium, the bar would have vibrated back and forth with a period of
(A) 4 seconds.
(B) 2 seconds.
(C) 0.5 seconds.
(D) 1 second.

Problem 22:

A taut (tightly stretched) string can experience
(A) standing waves but not traveling waves.
(B) neither standing waves nor traveling waves.
(C) traveling waves but not standing waves.
(D) both standing waves and traveling waves.

Problem 23:

When a home air conditioner is working properly, its working fluid is
(A) evaporating to a gas inside the home and condensing to a liquid outside the home.
(B) condensing to a liquid both inside and outside the home.
(C) evaporating to a gas both inside and outside the home.
(D) evaporating to a gas outside the home and condensing to a liquid inside the home.

Problem 24:

You wander into the kitchen on a dark, moonless night and open the refrigerator door. Sadly, the light bulb in the refrigerator has burned out and the kitchen remains pitch black. Just as you are about to reach for the carton of chocolate milk, your pet squirrel leaps onto your back and you twirl around several times before the squirrel heads off for some other part of the house. You have no idea which way you are facing. Fortunately, the refrigerator door is still open and you can feel the cold on your face as you turn in its direction. The physics explanation for this feeling of cold that you get when you face the refrigerator is that
(A) heat is flowing from the rest of the kitchen into the refrigerator and the pressure of this heat flow causes coldness to accumulate on the side of your body that's facing the refrigerator.
(B) the cold contents of the refrigerator do a much better job of absorbing your thermal radiation than do the warmer contents of the rest of the kitchen.
(C) you are radiating far more heat toward the cold contents of the refrigerator than they are radiating toward you.
(D) the cold contents of the refrigerator radiate coldness toward your skin and lower your skin's temperature.

Problem 25:

The second law of thermodynamics allows you to transfer heat from a colder object to a hotter object, but only if you accompany that transfer by a destruction of
(A) momentum from some other source.
(B) angular momentum from some other source.
(C) energy from some other source.
(D) order from some other source.

Problem 26:

You have invented a new variation of bowling in which you send the ball down the lane by hitting it with a mallet. The ball is stationary and you pound it forward to give it momentum. You have two mallets with identical masses: one with a head full of sand and one with a head made of highly elastic rubber. The sand mallet doesn't bounce off the ball, while the rubber mallet bounces almost perfectly. If you swing both mallets exactly the same way, you will find that
(A) the two mallets give the ball about the same forward momentum.
(B) the sand mallet will give the ball about twice as much forward momentum as the rubber mallet.
(C) only the rubber mallet gives the ball any forward momentum.
(D) the rubber mallet will give the ball about twice as much forward momentum as the sand mallet.

Problem 27:

You brought home a toy helium balloon this afternoon and already it has lost some of its helium. It is now hovering motionless at a constant height and is touching neither the ceiling nor the floor. The weight of air that the balloon is displacing is
(A) more than the weight of the balloon.
(B) zero.
(C) less than the weight of the balloon.
(D) exactly equal to the weight of the balloon.

Problem 28:

Cars that have trouble with "knocking" may require premium gasoline to run smoothly. The characteristic of premium gasoline that suppresses "knocking" is that premium gasoline is relatively
(A) hard to ignite.
(B) slippery and acts as a better lubricant.
(C) viscous and flows without turbulence.
(D) easy to ignite.

Problem 29:

For your art class, you are building a complicated kinetic structure with a single moving part. That moving part will have a stable equilibrium if there is an arrangement in which
(A) the net force (and net torque) is zero and from which any displacement will cause a decrease in total potential energy.
(B) the net force (and net torque) is zero and from which any displacement will cause a rise in total potential energy.
(C) the net force (and net torque) is minimum and from which any displacement will cause a rise in that net force (and net torque).
(D) the net force (and net torque) is maximum and from which any displacement will cause a decrease in that net force (and net torque).

Problem 30:

It's a windy day and you are standing in an enormous, open plaza. It's hard to keep your hat from blowing away. You find that when you stand just downwind of a huge, rigid abstract sculpture located at the center of the plaza, that you feel only a gentle swirling breeze instead of the overall wind. That's because the statue
(A) deflects the wind so that it misses you.
(B) creates a turbulent wake and you are standing in that wake.
(C) causes the air to experience laminar flow and you are standing in that flow.
(D) is extracting energy from the wind so that it is only barely moving.

Problem 31:

You throw a ball at the wall in front of you and the ball bounces directly back at you. While the ball is touching the wall, the horizontal force(s) the ball is experiencing is (are)
(A) the support force from the wall plus a forward force from the ball's momentum while it's coming to a stop.
(B) the support force from the wall plus a force from the ball's momentum that initially points forward, gradually reduces to zero as the ball stops, and then begins to point backward as the ball rebounds.
(C) only the support force from the wall.
(D) the support force from the wall plus a forward force from the ball's momentum throughout the bounce.

Problem 32:

An earthquake in the countryside can produce more than one distinct shaking motion at a distant city. These shaking motions are associated with different types of waves and may arrive at the city at slightly different times. Of these types of waves,
(A) 1 is a transverse wave and 2 are longitudinal waves.
(B) 2 are transverse waves and 1 is a longitudinal wave.
(C) 1 is a transverse wave and 1 is a longitudinal wave.
(D) 2 are transverse waves and 2 are longitudinal waves.

Problem 33:

The pendulum of a clock swings through its stable equilibrium rather than stopping at that equilibrium. To stop abruptly at the equilibrium point, the pendulum would have to get rid of what conserved quantity or quantities?
(A) Energy, but not momentum.
(B) Energy and momentum.
(C) Momentum, but not energy.
(D) Acceleration and velocity.

Problem 34:

The atoms in a sugar molecule are bound together, meaning that
(A) acceleration would be required to separate them.
(B) inertia would be required to separate them.
(C) momentum would be required to separate them.
(D) work would be required to separate them.

Problem 35:

You've missed a turn on a go-cart track and you're headed for disaster. You can crash into either a brick wall or a haystack. After a rapid review of all the physics you know, you decided to aim for the haystack. Good choice. Although either obstacle would have brought you to a complete stop, the haystack extracted
(A) the same amount of momentum from you that the brick wall would have, but while exerting less force on you.
(B) more momentum from you than the brick wall would have.
(C) less momentum from you than the brick wall would have.
(D) almost no momentum from you and thereby exerted less force on you than the brick wall would have.

Problem 36:

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 pushed back on Mike, but with less force than Mike exerted on him.
(B) Johnny pushed back on Mike, but with more force than Mike exerted on him.
(C) Johnny did push back on Mike, with exactly the same amount of force as Mike exerted on him.
(D) Johnny didn't push back on Mike.

Problem 37:

If your car didn't have shock absorbers, it would bounce up and down wonderfully on its spring suspension whenever you drove onto a curb. If you put more passengers into your car before driving onto that curb, the car would
(A) bounce at the same rate (same period).
(B) bounce faster (shorter period).
(C) bounce more slowly (longer period).
(D) become a taxi and you would have to apply for a taxi license and a cab medallion.

Problem 38:

A long-life bulb operates with its filament at a lower temperature than that of a standard light bulb. As a result of this low operating temperature, the long-life bulb
(A) emits redder light and is less energy efficient than a standard bulb.
(B) emits bluer light and is more energy efficient than a standard bulb.
(C) emits bluer light and is less energy efficient than a standard bulb.
(D) emits redder light and is more energy efficient than a standard bulb.

Problem 39:

Two separate pipes head to a bathroom sink side-by-side. One carries hot water and the other carries cold water. Hot water has more thermal energy per liter than cold water. Water is flowing at the same speed in each pipe and
(A) the pressure of the hot water is greater than that of the cold water.
(B) the pressure of the hot water is less than that of the cold water.
(C) the pressures in the two pipes do not have any relationship to one another.
(D) the pressure of the hot water is the same as that of the cold water.

Problem 40:

You are less likely to burn your hand on a pot with a stainless steel handle than on one with an aluminum handle. That's because stainless steel is
(A) a poorer thermal conductor than aluminum.
(B) hotter than aluminum.
(C) less dense than aluminum.
(D) shinier than aluminum.

Problem 41:

The water rising upward in a fountain has an upward velocity
(A) and an acceleration that is upward for the first half of the rise and downward for the second half of the rise.
(B) and an upward acceleration.
(C) and a downward acceleration.
(D) and a zero acceleration.

Problem 42:

Which of the following is not a harmonic oscillator:
(A) A person bouncing gently up and down on a stretched bungee cord.
(B) A car antenna bending back and forth.
(C) A bowling ball bouncing gently up and down on a trampoline.
(D) A yoyo going up and down on its string.

Problem 43:

A 100-watt light bulb has been operating for hours in a quiet, calm room and consumes 100 watts of electric power. The rate at which heat is flowing out of the bulb is
(A) about 100 watts.
(B) zero watts.
(C) significantly more than 100 watts.
(D) significantly less than 100 watts, but more than zero watts.

Problem 44:

Superheated water fails to boil because it is
(A) unable to form the initial bubbles needed for boiling.
(B) too hot to boil at atmospheric pressure.
(C) too viscous to boil at atmospheric pressure.
(D) too dense to boil at atmospheric pressure.

Problem 45:

To catch a ball well, you do best to let the ball push your hands backward as it hits. This motion of your hands lets the ball transfer more of its
(A) energy to your hands.
(B) force to your hands.
(C) acceleration to your hands.
(D) momentum to your hands.

Problem 46:

Your pendulum clock is running slow and you are arriving late to appointments. To speed up the pendulum and shorten its period, you should
(A) lengthen the pendulum.
(B) remove weight uniformly from the pendulum, while keeping its length the same.
(C) shorten the pendulum.
(D) add weight uniformly to the pendulum, while keeping its length the same.

Problem 47:

A kitchen mixer combines the ingredients best when its blades turn fairly rapidly through the batter you are making. If the blades turn too slowly, the various ingredients don't mix thoroughly, even if you wait a considerable amount of time. The advantage of rapid motion of the mixer blades reflects the need for
(A) viscosity to dominate the flow of batter in the mixer, so that the resulting laminar flow can fully combine the ingredients.
(B) viscosity to dominate the flow of batter in the mixer, so that the resulting turbulent flow can fully combine the ingredients.
(C) inertia to dominate the flow of batter in the mixer, so that the resulting laminar flow can fully combine the ingredients.
(D) inertia to dominate the flow of batter in the mixer, so that the resulting turbulent flow can fully combine the ingredients.

Problem 48:

The gas in the neck of a sealed champagne bottle is clear. It is essentially humid air at 100% relative humidity. After the cork pops out of a champagne bottle and flies across the room, this gas turns suddenly into a foggy mist. The gas transformed from clear to foggy because
(A) evaporation began to occur once the bottle was opened.
(B) it did work on the outgoing cork and experienced a drop in temperature. Water droplets condensed as a result of this temperature drop.
(C) tiny particles of cork were left behind in the air due to sliding friction with the bottle's walls.
(D) the cork's violent flight out of the bottle atomized some of the liquid champagne into a mist.

Problem 49:

Natural convection is used to heat food in a conventional electric oven. That convection is most efficient at conveying heat to the food when the oven's heating element is located
(A) above the food.
(B) below the food.
(C) beside the food.
(D) behind the food.

Problem 50:

You have 3 metal coins. They are identical except that one is shiny silver, one is black, and one is white. You put all 3 coins in a fire and heat them red hot. If they are all at the same temperature,
(A) the white one will glow most brightly.
(B) the silver one will glow most brightly.
(C) the black one will glow most brightly.
(D) they will all glow equally brightly.

PART II: SHORT ANSWER QUESTIONS

Please give a brief answer in the space provided. Part II is worth 33% of the grade on the final examination.

Problem 1:

Although the U.S. Patents Office tries not to issue patents for things that cannot possibly work, they aren't always successful in weeding out the nonsense. That's why they have hired you: to find the impossible claims and send their inventors packing. You're excited about the position and confident in your ability to distinguish fact from fiction.

(A) An inventor comes to you with a small box that's supposed to make batteries obsolete. The inventor claims that the box can produce electricity forever without having to be recharged. Its mechanical components supposedly twist one another in such a way that they keep each other turning indefinitely without any external help and can even generate electricity at the same time. You can be sure that this claim is nonsense because

(B) Another inventor comes in with a small motor-like device that supposedly soaks up thermal energy from the surrounding air and delivers it as electricity to a small power outlet on its side. Your knowledge of the laws of thermodynamics assures you that this claim, too, is nonsense because

(C) You can't seem to keep the con-artists and wackos from your door today! In walks another hypster who claims to have a heat pump that can transfer heat out of a can of sardines for as long as you like. The sardines just get colder and colder. Once again, you know that this is impossible because

(D) What a day! You are about to head home to tell your friends about the crazy crew you've been talking with when someone comes in with a glass vase that's supposed to automatically reassemble itself if you accidentally break it. You just have to put the broken vase in a box and wait. In a minute or two, the vase will be as good as new. You agree with the inventor that this reconstruction trick doesn't violate any of the laws of motion. However, you can still be sure that it won't work because

Problem 2:

According to all the designers in New York, Paris, and Milan, last year's colors are out and you'll have to repaint your room to match the new fall fashions. After replacing your entire wardrobe, you head off to the hardware store to buy matching paint.

(A) You select a particular can of paint and the salesperson opens it to check that it is still good. You notice that one of the paint's constituents has separated out and is floating on the top of the rest of the paint. What characteristic of that constituent is keeping it at the top of the can, rather than at the bottom?

(B) Many of the pigment particles are resting at the bottom of the can. When the can was first manufactured, those tiny solid particles were distributed evenly throughout the paint. However, as months passed they gradually settled to the bottom. What force slowed the descent of those solid pigment particles through the syrupy paint?

(C) To remix the paint, and make it homogeneous again, the salesperson mounts the sealed can in a shaking machine and lets the can jiggle back and forth violently for about a minute. The can's peak speed is never very high. You could make it go faster simply by dropping it from the store roof onto a foam pillow down below, but that wouldn't mix the paint very well. The paint can's velocity simply isn't important to the mixing process. What related physical quantity is essential to the mixing process?

(D) What type of flow does the paint experience during the mixing process and why does that improve the uniformity of the finished paint?

Problem 3:

You are an experienced rock-climber and are attempting to scale the face of a sheer granite cliff by yourself. Free climbing doesn't mean being foolish, so you carefully attach yourself to the rock every few feet as you ascend. Each attachment point is small gadget that you insert into a crack or opening and you bind yourself to that gadget with an elastic rope. If you were to fall, you would drop only about twice the distance between yourself and the nearest attachment point. You have been making steady progress all morning and are about half way up the face. You are standing still when suddenly your footing gives way and you begin to fall.

(A) Since the nearest attachment point is 1 meter below you when you start to fall, you descend 2 meters before the rope begins to pull tight. By the time you have dropped to that point, you have acquired lots of downward momentum. Where did that momentum come from and what transferred it to you?

(B) The rope is rather elastic and can easily stretch to about 7% more than its normal length. If the rope did not stretch, it might easily pull the attachment point out of the rock. Why is the stretchiness of the rope related to the force exerted on the attachment point during a fall?

(C) The rope successfully breaks your fall, but you end up bouncing around and swinging back and forth for a while. What conserved quantity are you having to get rid of in order to come to a stop?

(D) When you finally come to a stop, hanging there on the somewhat-stretched rope, what force (amount and direction) is the rope exerting on you? (Assume that you are not touching the rock face at all).

Problem 4:

You love spy movies and the latest Jaymes Bahnd movie is playing at the local theatre. You and your significant other pick up your extra large popcorn and wheel it down the aisle to your seats. The lights dim and you're soon immersed in the world of Jaymes Bahnd, secret agent number 006.95 plus tax. Naturally, Mr. Bahnd has lots of gadgets that do neat things, but some of them violate the laws of physics. Among the bloopers that you notice during this otherwise fabulous show are the following.

(A) To break into a private museum and recover the stolen medieval manuscript, Jaymes must enter the building and defeat all of its security systems. Jaymes decides to break into the building from its penthouse, 100 feet above the ground. He takes a small, lightweight pen from his pocket and clicks the button. A plume of rocket exhaust emerges from the other end of the pen and this midget rocket lifts Jaymes 100 feet in the air so that he lands easily in the penthouse garden. Why is the small weight of this pen incompatible with it lifting Jaymes off the ground?

(B) Bahnd plans to enter the building through its ventilation ducts. They will open when the temperature inside the penthouse apartment drops below 10 °C. Bahnd drills a small hole in the wall and lowers a small air conditioning device into the apartment on the end of its power cord. The unit consists only of a small box and its power cord. Jaymes plugs the cord into an outlet in the garden and the temperature inside the apartment begins to go down. Why can't you make such an air conditioner—one that uses only its connection to the power company to lower the temperature of the room in which it's placed?

(C) Once inside the building, Bahnd moves swiftly to the museum. He must slip past several sensors that see thermal radiation and can tell when a warmer body is moving through the halls. Bahnd slips on a black velvet robe and becomes impossible to see with your eyes in the darkened hallways. He goes right by the thermal sensors without them noticing. Sadly, the black velvet would not really help Jaymes hide from the thermal radiation sensors. Why not?

(D) To break the glass cabinet that contains the manuscript, Jaymes takes out a tiny tuning fork and hammer. He smacks the tuning fork with the hammer and holds the tuning fork to the microphone of the museum's public address system. The high-pitched tone travels briefly through the museum and all of the glass objects in that museum shatter. Why is it extraordinarily unlikely that even one glass object in the museum would shatter, let alone all of them?

Problem 5:

Nothing says romance like a candlelight dinner. You have just taken that gourmet tuna-noodle casserole out of the oven and are ready to serve it to your sweetie, but first you must light the candles.

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

(B) The candle wax begins to burn. Which molecules have stronger chemical bonds: (1) the wax and oxygen molecules before burning or (2) the water and carbon dioxide molecules that are formed as a result of burning?

(C) The candles emit a pleasant reddish-orange glow. The temperature in the candle flame is less than that of a normal light bulb's filament. How can you tell?

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

Problem 6:

The movie you were working on at the time of the midterm exam was a tremendous box-office success and you're working on the sequel! Once again, your heroine is going to rescue the hero from an unjust hanging. It's deja-vu all over again, but this time the screenwriters are going to be more careful to get the wording of the script clear. As this scene begins, the hero is standing still on a trapdoor high above the ground and there is what appears to be a rope around his neck. Of course, the heroine has again replaced the rope with an elastic bungee cord.

(A) Consider the exact moment when the trapdoor opens and there is suddenly nothing under the hero's feet. The bungee cord is at its equilibrium length and is not pulling on anything yet. At that exact moment, the instant in time when the trapdoor has vanished, the hero is experiencing what (1) net force, (2) velocity, and (3) acceleration? (report specific values for these three quantities)

(B) Because it's a bungee cord rather than a rope, the cord tenses gradually as the hero descends for the first time. At what point in this first descent does the hero reach his maximum downward velocity?

(C) The heroine gallops up on a white horse, passing right under the hero as he descends for the first time. He slows to a stop just as she reaches him and she cuts the cord from his neck. At the moment he stopped descending (and she cut him free), was the hero accelerating vertically and, if so, which way?

(D) The elastic cord snaps upward violently after being cut and it knocks the evil sheriff off the platform (the judge from the first movie is still in the hospital). Clearly, the cord has enormous kinetic energy at the end of the scene. What form was that energy in at the beginning of the scene—when the hero was standing on the closed trapdoor?