Problem 1:
During the power stroke in an internal combustion engine, the hot burned gases inside the cylinder push the piston out of the cylinder. As the piston moves out of the cylinder,
(A) the temperature but not the pressure of the hot burned gases decreases.
(B) the pressure but not the temperature of the hot burned gases decreases.
(C) neither the pressure nor the temperature of the hot burned gases decreases.
(D) both the pressure and the temperature of the hot burned gases decrease.
Problem 2:
An astronaut hovering in the middle of the space shuttle's cabin as it orbits the earth is
(A) not accelerating.
(B) accelerating directly toward the center of the earth.
(C) accelerating horizontally in the direction of the orbit.
(D) accelerating horizontally in the direction opposite the orbit.
Problem 3:
Someone has dropped a beach ball out of an airplane and it is descending toward the earth. The air pressure just beneath it as it descends is
(A) zero.
(B) equal to atmospheric pressure.
(C) less than atmospheric pressure.
(D) greater than atmospheric pressure.
Problem 4:
When you pour water, it easily becomes turbulent. In contrast, when you pour honey it rarely becomes turbulent. Honey resists turbulence because
(A) its high viscosity (thickness) allows viscous forces to keep the flow orderly.
(B) its high elastic potential energy allows it to maintain a stable equilibrium.
(C) its high density (mass per volume) allows inertia to keep the flow orderly.
(D) its high weight per volume allows gravity to keep the flow orderly.
Problem 5:
You're at the county fair, watching people try to win prizes by tossing small hard-plastic rings onto the necks of glass soda bottles. The rings keep bouncing off the bottles and no one ever wins. What makes the game so hard to win is that the rings are unable to get rid of
(A) either their momentum or their energy.
(B) their energy, but they transfer momentum easily to the bottles.
(C) their momentum, but they transfer energy easily to the bottles.
(D) their mass.
Problem 6:
You are building a decorative mobile and the first thing you do is hang a long stiff rod from a string attached to the ceiling. When you have properly centered the string on the rod, the rod experiences zero torque about its center of mass. With zero net torque acting on it, the rod
(A) is horizontal and motionless.
(B) is horizontal or tilted, and motionless.
(C) experiences zero angular velocity.
(D) experiences zero angular acceleration.
Problem 7:
During your trip to the mountains, you put water on the stove to boil. You find that it boils at a lower temperature than usual because
(A) the decreased atmospheric pressure at high altitude allows the air bubbles in boiling water to expand and grow more quickly.
(B) gravity is slightly weaker as you move farther from the center of the earth.
(C) the decreased atmospheric pressure at high altitude lets bubbles of pure steam survive at lower temperatures.
(D) gravity is slightly stronger as you move farther from the center of the earth.
Problem 8:
You are living in an old house with aged plumbing. The pressure in the water main outside the house is good and steady, but the shower spray is surprisingly weak. And when other people are running water at the same time, the shower barely sprays at all. The reason that the shower spray is so weak while other people are running water is that
(A) everyone in the house has to share the water's energy, so the shower gets less of the total energy.
(B) everyone in the house has to share the water's momentum, so the shower gets less of the total momentum.
(C) speeding up the water flow in the pipes causes it to turn an even larger fraction of its total energy into thermal energy through viscous effects.
(D) everyone in the house has to share the water pressure, so the shower gets less of the total pressure.
Problem 9:
The glass envelope of an incandescent light bulb contains
(A) an inert gas mixture that increases the bulb's energy efficiency.
(B) an excellent vacuum that prolongs the life of its filament.
(C) an inert gas mixture that prolongs the life of its filament.
(D) an excellent vacuum that increases the bulb's energy efficiency.
Problem 10:
Water is flowing gently out of the end of a garden hose. You block off most of hose's opening with your thumb and now the water sprays out at high speed because you
(A) are doing work on the water with your thumb and greatly increasing its total energy.
(B) are keeping air from getting into the hose and reducing the pressure.
(C) are compressing the water and increasing its density.
(D) have slowed the water flow through hose so that it wastes less energy doing working against viscous forces.
Problem 11:
While an airplane is flying at constant velocity, the average air pressure under its wings is
(A) lower than the average air pressure above its wings.
(B) higher than the average air pressure above its wings.
(C) the same as the average air pressure above its wings.
(D) atmospheric pressure.
Problem 12:
Heat naturally flows from a hot object to a cold object because
(A) of Newton's first law of motion.
(B) of Newton's second law of motion.
(C) of Newton's third law of motion.
(D) that is the statistically most likely direction of heat flow.
Problem 13:
You have just leapt off the high diving board and are falling. Neglecting any effects due to air, which of the following quantities can't change while you are above the water?
(A) Your angular momentum.
(B) Your momentum.
(C) Your gravitational potential energy.
(D) Your kinetic energy.
Problem 14:
Ice cubes gradually shrink in a frost-free freezer because
(A) water molecules go directly from solid ice to gaseous water vapor.
(B) the freezer gremlin likes to nibble on the ice cubes.
(C) the ice melts periodically and some of it drips into the bottom of the freezer.
(D) the ice melts periodically and some of it evaporates before it can refreeze.
Problem 15:
Your shampoo bottle is almost empty, so you tighten its cap and swing it rapidly in a circle with its cap end pointing outward. The remaining shampoo collects just inside the cap and you are able to squeeze out one more dollop. This technique works because
(A) viscous forces push the shampoo toward the cap end of the bottle.
(B) centrifugal force pushes the shampoo toward the cap end of the bottle.
(C) the force of the shampoo's momentum pushes it toward the cap end of the bottle.
(D) the bottle's rapid inward acceleration leaves the shampoo behind so that it drifts toward the cap end of the bottle.
Problem 16:
Standing up in a canoe is a poor idea because the canoe can easily tip over. When you are seated low in the canoe, it is stable because any tip will
(A) lower its center of gravity and increase its total potential energy.
(B) raise its center of gravity and increase its total potential energy.
(C) raise its center of gravity and decrease its total potential energy.
(D) lower its center of gravity and decrease its total potential energy.
Problem 17:
An electric generating plant uses hot, high-pressure steam to power its generators. This steam engine can become more energy efficient as the temperature of its steam increases because
(A) hotter steam has more energy.
(B) hotter steam has more entropy.
(C) hotter steam has less entropy.
(D) the efficiency of any heat engine increases as the temperature between its heat source (the hot object) and its heat destination (the cold object) grows larger.
Problem 18:
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
(A) you gave it a rightward push as it came out of your fingers.
(B) it is deflecting the airflow around it to your left.
(C) it is deflecting the airflow around it to your right as well.
(D) the pressure in front of it is higher than the pressure behind it.
Problem 19:
A fountain is spraying a clear stream of water in a high arc so that it falls gracefully into a distant pool. After the water has left the fountain's nozzle and while it is arcing through the open air, it
(A) converts kinetic energy into pressure potential energy and then pressure potential energy into kinetic energy.
(B) converts kinetic energy into gravitational potential energy and then pressure potential energy into kinetic energy.
(C) converts kinetic energy into pressure potential energy and then gravitational potential energy into kinetic energy.
(D) converts kinetic energy into gravitational potential energy and then gravitational potential energy into kinetic energy.
Problem 20:
You are an Opera star and are attending a gala dinner to celebrate your accomplishments. To give the guests a thrill, you demonstrate your ability to break a wineglass with your voice. You tap the glass and listen to its vibrational pitch. To break the glass, you hold it near your mouth and sing loudly at
(A) its vibrational pitch.
(B) a pitch just below its vibrational pitch.
(C) a pitch just above its vibrational pitch.
(D) a pitch that is exactly twice its vibrational pitch.
Problem 21:
You have thrown a stone toward the pond in front of you and it is now at the highest point in its arc. Neglecting any forces due to air, the net force on the stone
(A) points straight downward.
(B) points down and forward.
(C) points straight forward.
(D) is zero.
Problem 22:
A tall pine tree sways back and forth on a windy day. A bunch of squirrels decide to hold their annual convention in that tree and climb up to the top. When they do, the tree's swaying motion
(A) decreases in amplitude; the tree sways less far.
(B) becomes slower; its period of motion increases.
(C) becomes faster; its period of motion decreases.
(D) increases in amplitude; the tree sways farther.
Problem 23:
Two children are swinging side by side on identical playground swings. The heavier one weighs twice as much as the lighter one. As they swing back and forth, you notice that
(A) the two children swing with the same period.
(B) the heavier child swings with a longer period than the lighter child.
(C) there is no relationship between the periods of their swings.
(D) the heavier child swings with a shorter period than the lighter child.
Problem 24:
You put a glass of water on the floor of a large room full of dry air. The room is so perfectly insulated that no heat flows in or out of it. A day later, the glass is empty and the room air is moist. Compare the total entropy of the earlier situation (full glass plus dry room air) to the total entropy of the later situation (empty glass plus moist room air).
(A) The total entropy of the later situation is lower than the entropy of the earlier situation.
(B) The two situations have equal total entropy because no heat entered the room.
(C) The two situations have equal total entropy because total entropy is conserved.
(D) The total entropy of the later situation is higher than the entropy of the earlier situation.
Problem 25:
A kiln is used to fire pottery—to heat it red or even yellow hot so that it fuses into a hard, finished ceramic. You have four pots to fire, each with its own surface color. One is black, one is white, one is shiny aluminum-like, and one is essentially transparent. You place the four pots in a kiln and heat them to the same yellow-hot temperature. When you look inside the kiln, the one that is glowing most brightly is the one that is
(A) white.
(B) black.
(C) shiny aluminum-like.
(D) essentially transparent.
Problem 26:
To turn left, an airplane dips its left wing slightly. By tipping in that manner, the airplane is using
(A) its aerodynamic drag to push it to the left.
(B) air friction to push it to the left.
(C) gravity to push it to the left.
(D) its aerodynamic lift to push it to the left.
Problem 27:
On a hot, humid day, your moist, sweaty skin doesn't do a very good job of cooling you off. If the air were less humid, you'd cool off better because water molecules would
(A) land on your moist skin more often.
(B) leave your moist skin more often.
(C) leave your moist skin less often.
(D) land on your moist skin less often.
Problem 28:
You are rearranging the furniture and are moving your desk to the other side of the room. To keep your desk sliding across the level floor at constant velocity, you have to keep pushing it forward. The net force on the desk is
(A) forward and proportional to the velocity at which the desk is moving.
(B) forward because the forward force you are exerting on the desk is larger than the backward force that friction is exerting on the desk.
(C) forward and proportional to the speed at which the desk is moving.
(D) zero, even though the ground is exerting a backward frictional force on the desk.
Problem 29:
You are sitting still in your airplane seat, holding your mp3 player in your hand, when the airplane begins to rise to a higher altitude. As the plane rises, you are
(A) doing zero work on your mp3 player.
(B) doing positive work on your mp3 player.
(C) lifting the plane up all by yourself.
(D) doing negative work on your mp3 player.
Problem 30:
You're standing on the middle of the Ruffner Hall pedestrian bridge when a group of prospective students jumps up and down and sets the bridge bouncing. As you bounce up and down about equilibrium, your acceleration is greatest when you are
(A) passing through equilibrium on your way downward.
(B) half way between the top and bottom of the bounce.
(C) at the top and bottom of the bounce.
(D) passing through equilibrium on your way upward.
Problem 31:
Two marbles are in a large bowl and the system is completely isolated from its surroundings. Each of the four arrangements listed below as possible answers contains exactly the same amount of total energy, although that energy may be in different forms in the different arrangements. Which arrangement has the most entropy?
(A) The marbles high up on the same side of the bowl, but not touching.
(B) The marbles both rolling quickly through the bottom of the bowl, but not touching.
(C) The marbles resting motionless in the bottom of the bowl.
(D) The marbles high up on opposite sides of the bowl.
Problem 32:
When you strike a match on the side of the match box, you are using sliding friction to
(A) melt the wax on the match and allow it to mix with the wood or paper.
(B) provide the activation energy needed to initiate the chemical reactions of combustion.
(C) push away the protective cap on the match to expose the thermal energy underneath.
(D) wear away the protective cap on the match to expose the burning surface underneath.
Problem 33:
It's hard to stand a coin on its edge. However, if you roll a coin forward on its edge, it stays up easily. The rolling coin is
(A) automatically steering itself under its center of gravity and is thus dynamically stabilized.
(B) in a stable equilibrium.
(C) supported by sliding friction.
(D) supported by static friction.
Problem 34:
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
(A) does not flow at all.
(B) flows from the copper pot to the fabric mat.
(C) flows from whichever is the more massive to whichever is the less massive.
(D) flows from the fabric mat to the copper pot.
Problem 35:
Two people have just bungee-jumped simultaneously and are now bouncing gently beside one another. The heavier person weighs twice as much as the lighter person and is hanging from two standard bungee cords while the lighter person is hanging from just one standard cord. As the two people bounce, they notice that
(A) there is no relationship between their bouncing rates.
(B) the heavier person is bouncing twice as often as the lighter person.
(C) the lighter person is bouncing twice as often as the heavier person.
(D) they are bouncing equally often.
Problem 36:
You are a passenger in a car that is making a sharp left turn. A book on the dashboard begins sliding toward the right because
(A) inertia trying to make it continue straight ahead as the car moves leftward.
(B) centrifugal force pushes the book toward the right.
(C) sliding friction pushes the book toward the right.
(D) static friction pushes the book toward the right.
Problem 37:
Compared to a smooth golf ball, a dimpled golf ball produces
(A) a faster-moving turbulent wake behind it as it flies.
(B) a slower-moving turbulent wake behind it as it flies.
(C) a smaller turbulent wake behind it as it flies.
(D) a larger turbulent wake behind it as it flies.
Problem 38:
You're blowing across the mouth of a bottle and it's whistling loudly with a clear tone. If you replace the air in the bottle with helium and again blow across the mouth of the bottle, its tone will be
(A) louder in volume, but will quickly return to normal as the helium escapes.
(B) softer in volume, but will quickly return to normal as the helium escapes.
(C) lower in pitch, but will quickly return to normal as the helium escapes.
(D) higher in pitch, but will quickly return to normal as the helium escapes.
Problem 39:
When your home air conditioner is working, the air in your room is being cooled by passing it by
(A) a condenser, in which a working fluid is turning from a gas to a liquid.
(B) an evaporator, in which a working fluid is turning from a liquid to a gas.
(C) a confounder, in which a working fluid is being asked difficult questions.
(D) a compressor, in which a working fluid is being squeezed into a smaller space.
Problem 40:
Your home is heated by a heat pump that transports heat from the outdoor air to the indoor air. As this device operates,
(A) it delivers more heat to the indoor air than it removes from the outdoor air.
(B) the thermal energy it delivers to the indoor air is equal to the electric energy it consumes.
(C) it delivers less heat to the indoor air than it removes from the outdoor air.
(D) it delivers the same amount of heat to the indoor air as it removes from the outdoor air.
Problem 41:
In a spaceship that is orbiting the earth with its rockets off, one of the mechanisms of heat transfer no longer works well:
(A) radiation.
(B) convection.
(C) the US postal service.
(D) conduction.
Problem 42:
You are trapped in an elevator car that is out of control. It won't stop moving for more than an instant and is going up and down randomly. At this moment, you are feeling extremely heavy, so you must be
(A) accelerating downward.
(B) accelerating upward.
(C) moving upward.
(D) moving downward.
Problem 43:
An empty glass bottle with its cap screwed on tightly is floating on a still lake. The bottle's weight is equal to the weight of
(A) the air it contains.
(B) the water it is displacing.
(C) the water it could hold if you filled it.
(D) the mixture of water and air that it is displacing.
Problem 44:
As you push a child on a swing, you can increase the amplitude of the motion by pushing the child away from you whenever she is
(A) accelerating away from you.
(B) moving away from you.
(C) moving toward you.
(D) accelerating toward you.
Problem 45:
You are weighing yourself on a bathroom scale. It reads your correct weight up until the moment you jump off the scale. For that brief time, the scale reads heavier than your weight because the scale is pushing up on you with a force
(A) equal to your weight, but you are accelerating upward.
(B) greater than your weight, but you are not accelerating.
(C) greater than your weight and you are accelerating upward.
(D) equal to your weight, but you are pushing downward with a force greater than your weight.
Problem 46:
Water is sloshing back and forth gently in your aquarium. You shake the aquarium until the water is sloshing twice as strongly. The period of the slosh—the time it takes to complete a full cycle of motion—is now
(A) twice as long as it was earlier.
(B) half as long as it was earlier.
(C) about 1.414 times as long as it was earlier.
(D) the same as it was earlier.
Problem 47:
You're floating on a raft in the open ocean. As the waves move forward underneath the raft, you move
(A) forward at a speed proportional to the wavelength of the waves.
(B) forward at a speed proportional to the height of the waves.
(C) forward at the speed of the wave crests.
(D) in a circle, without making any net progress forward.
Problem 48:
While an airplane is flying at constant velocity, the downward momentum it transfers to the passing air each second is
(A) zero.
(B) equal to the downward momentum transferred to it by gravity each second.
(C) greater that the downward momentum transferred to it by gravity each second.
(D) less than the downward momentum transferred to it by gravity each second.
Problem 49:
The maximum speed of a rocket-propelled spaceship with an exhaust speed of 5000 mph is
(A) 2500 mph.
(B) 5000 mph.
(C) limited only by the ratio of fuel to spaceship.
(D) 10000 mph.
Problem 50:
Compared to regular gasoline, premium or high-octane gasoline
(A) is harder to ignite and therefore more resistant to knocking.
(B) contains far more thermal energy and therefore provides your car with much more power.
(C) is easier to ignite and therefore more resistant to knocking.
(D) contains far more chemical potential energy and therefore provides your car with much more power.
Problem 51:
You turn on the refrigerator in your dorm room and it begins cooling the food inside it. The refrigerator cools the food by
(A) converting the food's thermal energy into electricity and using that electricity to operate its fan.
(B) converting the food's thermal energy into potential energy and letting that potential energy fall into the pan underneath the refrigerator.
(C) using electricity to pump the food's thermal energy into your dorm room.
(D) converting the food's thermal energy into useful work and using that work to operate its compressor.
Problem 52:
A spacecraft in deep space is coasting directly toward Sirius, the dog star. To change its course, it fires its rocket thruster at right angles to its direction of travel. After this procedure, the total momentum of the spacecraft plus its original fuel now points
(A) directly away from Sirius.
(B) somewhere between the direction that the rocket is now heading and the direction in which it used to head.
(C) in the direction that the spacecraft itself is now heading.
(D) directly toward Sirius.
Problem 53:
It's a cold day and you are standing just inside the front door of your house. A guest opens the door so that you can see the neighbors' houses. Before any cold air reaches you, you already begin to feel colder because
(A) the outdoor objects are farther from you than the front door.
(B) the cold outdoor objects radiate less heat toward you than the warm front door did.
(C) the outdoor objects are larger than the front door and therefore absorb more heat from you.
(D) you radiate more heat toward the cold outdoor objects than you did toward the warm front door.
Problem 54:
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 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. Now the water rises to the
(A) 6th floor.
(B) 8th floor.
(C) 9th floor.
(D) 10th floor.
Problem 55:
During the compression stroke in an internal combustion engine, the piston squeezes the mixture of fuel and air into a small volume inside the cylinder. As the piston moves into the cylinder,
(A) neither the pressure nor the temperature of the fuel and air mixture increases.
(B) the temperature but not the pressure of the fuel and air mixture increases.
(C) the pressure but not the temperature of the fuel and air mixture increases.
(D) both the pressure and the temperature of the fuel and air mixture increase.
Problem 56:
To propel itself forward, a rocket pushes against
(A) its own exhaust.
(B) the air through which it travels.
(C) the launch pad.
(D) the earth.
Problem 57:
After its rider has fallen off it, a skateboard rolls directly up a ramp, comes to a stop, and rolls back down. During its travel along the ramp, the skateboard accelerates
(A) uphill at a slower and slower rate until its acceleration reaches zero at the top of the ramp and then downhill at a faster and faster rate.
(B) steadily downhill.
(C) straight down.
(D) steadily uphill on its way up the ramp and steadily downhill on its way down the ramp.
Problem 58:
The air leaving a jet engine has
(A) more backward momentum than it had when it entered the jet engine.
(B) less backward momentum than it had when it entered the jet engine.
(C) no backward momentum.
(D) the same backward momentum as it had when it entered the jet engine.
Problem 59:
When you operate the broiler of your electric oven, only the heating element at the top of the oven becomes hot. As you broil vegetables in the middle of the oven, those vegetables are heated primarily by
(A) evaporation.
(B) convection.
(C) conduction.
(D) radiation.
Problem 60:
Your bottle of oil and vinegar salad dressing has separated, so that the oil is floating on the vinegar. You notice that a large herb is floating motionless at the interface between the oil and the vinegar. That herb's average density is
(A) more than that of either vinegar or oil.
(B) less than that of either vinegar or oil.
(C) less than that of oil but more than that of vinegar.
(D) less than that of vinegar but more than that of oil.
Problem 61:
Tightening a violin string
(A) stiffens the string's restoring forces, but leaves the frequencies of its vibrational modes unchanged.
(B) reduces the string's weight, but leaves the frequencies of its vibrational modes unchanged.
(C) reduces the string's inertia and decreases the frequencies of its vibrational modes.
(D) stiffens the string's restoring forces and increases the frequencies of its vibrational modes.
Problem 62:
As a large wave approaches the beach, its crest suddenly dives over the water in front of it and breaks up into white froth. This diving surf occurs when
(A) friction with the sandy beach slows the bottom of the wave and it moves out from under the crest.
(B) the wave's wavelength has become longer that the distance to the beach.
(C) the wind is so strong that it blows the wave crest over the trough in front of it.
(D) the water has become too shallow to form a complete wave crest.
Problem 63:
You're hanging clothes on a clothesline that is strung tightly between two posts and you notice that the clothesline tends to vibrate up and down in its fundamental mode. As you add clothes to the clothesline, the period of that fundamental vibration
(A) increases.
(B) decreases.
(C) remains constant, but only if the amplitude of the vibration remains constant.
(D) remains constant even if the amplitude of the vibration changes.
Problem 64:
Your hanging birdfeeder swings gently back and forth like a pendulum. If a gust of wind starts it swing with twice its current amplitude, the period of its swing will
(A) increase by a factor of about 1.414.
(B) remain unchanged.
(C) double.
(D) halve.
Problem 65:
An operating internal combustion engine can't avoid releasing some waste heat into its environment because
(A) entropy is conserved.
(B) converting all of the heat into work would violate the laws of thermodynamics.
(C) energy is always increasing.
(D) heat always flows from hotter to colder objects.
Problem 66:
Your friend has purchased a thin cooking pot made entirely of stainless steel. Your friend places this pot on the coil burner of an electric stove and tries to cook risotto. To your friend's dismay, the risotto cooks very unevenly and burns at various places on the bottom of the pot. The pot's problem is that stainless steel is a
(A) poor absorber of heat and therefore a poor conductor of heat.
(B) poor conductor of both electricity and heat.
(C) good absorber of heat and therefore a poor conductor of heat.
(D) good conductor of electricity and therefore a poor conductor of heat.
Problem 67:
When an airplane lifts its nose too high while flying forward,
(A) the airstream separates from the bottoms of its wings and the airplane experiences more lift and less drag.
(B) the airstream separates from the tops of its wings and the airplane experiences less lift and more drag.
(C) the airstream separates from the tops of its wings and the airplane experiences more lift and less drag.
(D) the airstream separates from the bottoms of its wings and the airplane experiences less lift and more drag.
Problem 68:
The "A" string of a guitar normally vibrates 440 times per second in its fundamental mode. If you hold the middle of that string so that it can't move and pluck one of the half-strings, its main vibration will occur at
(A) 440 times per second.
(B) 220 times per second.
(C) 660 times per second.
(D) 880 times per second.
Problem 69:
You are bouncing gently on a springboard before diving into the water. While your feet remain on the board's surface, the period of your bounce is independent of the height of that bounce. But once your feet start leaving the board, the period of your bounce increases because
(A) the stiffness of the board decreases while you are in the air.
(B) the restoring force pushing you back toward equilibrium is no longer proportional to your displacement from equilibrium; it is too strong while you are in the air.
(C) the restoring force pushing you back toward equilibrium is no longer proportional to your displacement from equilibrium; it is too weak while you are in the air.
(D) the stiffness of the board increases while you are in the air.
Problem 70:
Your desk lamp has a dimmer switch so that you can reduce the power going to its incandescent bulb. If you reduce the power going to the bulb by 50%, it will emit
(A) less than 50% as much visible light as before.
(B) more than 50% as much visible light as before.
(C) 50% as much visible light as before, but with a redder appearance.
(D) 50% as much visible light as before, but with a darker appearance.
Problem 71:
Many hospitals measure patients' temperatures by inserting optical devices into their ears. Those devices sense temperature with light by
(A) reflecting light from the ear canal. A dimmer reflection means a hotter ear.
(B) looking at the spectrum of wavelengths emitted by the ear canal. Longer wavelengths mean a hotter ear.
(C) looking at the spectrum of wavelengths emitted by the ear canal. Shorter wavelengths mean a hotter ear.
(D) reflecting light from the ear canal. A brighter reflection means a hotter ear.
Problem 72:
Your glass cup contains a mixture of ice and water. It's a warm day and heat is flowing into that glass. As the heat enters the mixture of ice and water, the temperature of the mixture
(A) increases in proportion to the remaining ice as the ice gradually converts to liquid water.
(B) remains constant, but the ice gradually converts to liquid water.
(C) increases steadily as the ice gradually converts to liquid water.
(D) remains constant, but the liquid water gradually converts to ice.
Problem 73:
You and your best friend are trying to pull one another toward your respective dorm rooms. You're the stronger of the two and, with a mighty tug, you drag your friend into your room. As you are pulling your friend toward your room, the force you exert on your friend is
(A) less in amount than the force your friend exerts on you.
(B) equal in amount to the force your friend exerts on you.
(C) zero.
(D) greater in amount than the force your friend exerts on you.
Problem 74:
The plastic tube carrying water to a fountain has a bulge. As the rapidly flowing water in the tube enters this unusually wide part of the tube, it
(A) speeds up and its pressure rises.
(B) speeds up and its pressure drops.
(C) slows down and its pressure drops.
(D) slows down and its pressure rises.
Problem 75:
Compared to the filament of a 50 watt light bulb, the filament of a 100 watt light bulb operates at
(A) the same temperature but has twice as much surface area.
(B) about 1.414 times the temperature.
(C) twice the temperature.
(D) half the temperature.
Problem 76:
If the earth's gravity became stronger, waves on the open ocean would travel
(A) at the same speed as with normal gravity, but with lower crests.
(B) slower than with normal gravity.
(C) at the same speed as with normal gravity, but with higher crests.
(D) faster than with normal gravity.
Problem 77:
You add 1 joule of heat to a cold object and 1 joule of heat to a hot object. As a result of these additions,
(A) the cold object experiences a greater rise in entropy than the hot object.
(B) the hot object experiences a greater rise in entropy than the cold object.
(C) neither object experiences a rise in entropy.
(D) the two objects experience equal rises in entropy.
Problem 78:
You live on a small island and it is now high tide. Your friend lives on another small island, exactly on the opposite side of the earth from your island. On your friend's island, it is now
(A) low tide.
(B) high tide.
(C) between high and low tide, with the water level rising.
(D) between high and low tide, with the water level dropping.
Problem 79:
If you use a microwave oven to heat clean water in a smooth glass container, you can sometimes superheat the water—that is, raise its temperature well above water's boiling temperature without it boiling. In that case, the very hot water fails to boil because
(A) even though bubbles of pure steam are stable at such high temperatures, they cannot form without help.
(B) bubbles of pure steam shrink quickly when they are exposed to atmospheric pressure, even at such high temperatures.
(C) bubbles of pure steam must stick to the surface of a container in order to grow in size, but slick glass surfaces won't hold these bubbles in place long enough for boiling to occur.
(D) bubbles of pure steam are not stable in clean water that is uniformly heated, even at such high temperatures.
Problem 80:
You drop a can of soup 10 feet onto a cement floor and it hits squarely on the bottom end of that can. The impact is likely to
(A) make the sides of the can bulge outward near the bottom end of the can.
(B) make the sides of the can bulge inward near the bottom end of the can.
(C) make the sides of the can bulge outward near the top end of the can.
(D) make the top end of the can bulge upward.