Final Exam 2010
You place three nonflammable objects among the red-hot coals of a roaring fire. The objects are identical in shape and size, but one object is black, another is white, and the third is shiny silver. After a few minutes, all three objects are at the same temperature: 1800 °C. They remain solid and are now glowing with thermal radiation. Which one is glowing most brightly? (A) The object that original appeared black. (B) The object that originally appeared silver. (C) The object that originally appeared white. (D) They are all glowing with equal brightness.
(A) The object that original appeared black.
Two identical rooms at identical temperatures contain identical collections of atoms. In one room that collection consists of moist air and an empty bowl and in the other room that collection consists of dry air and a bowl full of water. Which of the two rooms has the greater entropy (disorder)? (A) The room containing moist air and an empty bowl has the greater entropy. (B) The two rooms have equal entropies because they have identical temperatures. (C) The two rooms have equal entropies because they contain identical collections of atoms. (D) The room containing dry air and the full bowl has the greater entropy.
(A) The room containing moist air and an empty bowl has the greater entropy.
Water is flowing smoothly through a garden hose that rests on level ground. The hose bends toward the left and the water follows that bend. Neglecting any effects due to the water's viscosity, compare the water just inside the left and right sides of that bend. (A) Water on the left side has lower pressure and higher speed than water on the right side. (B) Water on the left side has lower pressure and lower speed than water on the right side. (C) Water on the left side has higher pressure and lower speed than water on the right side. (D) Water on the left side has higher pressure and higher speed than water on the right side.
(A) Water on the left side has lower pressure and higher speed than water on the right side.
A cup of water is in thermal equilibrium. If you stir the water vigorously, the water will become hotter. What causes this rise in temperature? (A) You do work as you stir the water and that work becomes thermal energy in the turbulent liquid. (B) You are making the water move as though it were boiling, so that it becomes hotter. (C) You are encouraging the conduction of heat from the cup to the water. (D) You are forcing convection to occur so that heat flows more rapidly from the cup to the water.
(A) You do work as you stir the water and that work becomes thermal energy in the turbulent liquid.
If you try to cook vegetables with 100 °C air, it takes a long time. But if you cook those same vegetables with 100 °C steam, they cook quickly. This is because the steam (A) condenses on the colder vegetables and releases a large amount of heat to the vegetables. (B) condenses on the colder vegetables and absorbs a large amount of heat from the vegetables. (C) causes moisture inside the vegetables to boil and transfer heat to the vegetables. (D) causes moisture inside the vegetables to boil and absorb heat from the vegetables.
(A) condenses on the colder vegetables and releases a large amount of heat to the vegetables.
An air conditioner is cooling the air inside your house on a hot summer day. As a result of the air conditioner's operation, the entropy (disorder) of the indoor air is (A) decreasing, the entropy of outdoor air is increasing, and the total entropy of both is increasing. (B) decreasing and the entropy of outdoor air is decreasing. (C) increasing, the entropy of outdoor air is decreasing, and the total entropy of both is increasing. (D) increasing and the entropy of outdoor air is increasing.
(A) decreasing, the entropy of outdoor air is increasing, and the total entropy of both is increasing.
A satellite is orbiting the earth in a not-quite-circular orbit. As it moves, the satellite is accelerating (A) directly toward the center of the earth. (B) nearly forward, in the direction of a perfect circle around the earth. (C) directly outward, away from the center of the earth. (D) exactly forward, in the direction that the satellite is heading.
(A) directly toward the center of the earth.
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 fabric mat to the copper pot. (C) flows from the copper pot to the fabric mat. (D) flows from whichever is the more massive to whichever is the less massive.
(A) does not flow at all.
Water is flowing gently out of the end of a garden hose. You block off most of the hose's opening with your thumb and now the water sprays out at high speed because you (A) have slowed the water flow through hose and plumbing so that the water wastes less energy doing work against viscous forces. (B) are doing work on the water with your thumb and greatly increasing its total energy. (C) are compressing the water and increasing its density. (D) are keeping air from getting into the hose and reducing the pressure.
(A) have slowed the water flow through hose and plumbing so that the water wastes less energy doing work against viscous forces.
Wearing a thin nylon jacket with no additional insulation still helps you stay warm on a cold, windy day. The primary way in which the jacket keeps you warm is by (A) helping you retain a thin layer of warm air near your skin. (B) preventing radiation from transferring heat from your skin to your surroundings. (C) increasing the overall pressure drag force you experience from the wind. (D) preventing conduction from transferring heat from your skin to your surroundings.
(A) helping you retain a thin layer of warm air near your skin.
One warm spring day you and some friends go to the beach at a nearby lake. You are playing with an almost fully inflated beach ball, which has a limp, floppy skin that dents effortlessly when you push on it. Someone accidentally throws the ball it into the ice cold lake. The ball appears to deflate partly on contact with the freezing water, although it has no leak. The large decrease in the ball's temperature caused a large (A) increase in the density of the air inside the ball. (B) increase in the pressure of the air inside the ball. (C) decrease in the pressure of the air inside the ball. (D) decrease in the density of the air inside the ball.
(A) increase in the density of the air inside the ball.
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) it is deflecting the airflow around it toward your left. (B) the pressure in front of it is higher than the pressure behind it. (C) you gave it a rightward push as it came out of your fingers. (D) it is deflecting the airflow around it toward your right as well.
(A) it is deflecting the airflow around it toward your left.
When an airplane is in level flight at 30,000 feet and moving at constant velocity, the average air pressure just above its wings is (A) less than atmospheric pressure and the average air pressure just below its wings is more than atmospheric pressure. (B) more than atmospheric pressure and the average air pressure just below its wings is less than atmospheric pressure. (C) less than atmospheric pressure and the average air pressure just below its wings is less than atmospheric pressure. (D) more than atmospheric pressure and the average air pressure just below its wings is more than atmospheric pressure.
(A) less than atmospheric pressure and the average air pressure just below its wings is more than atmospheric pressure.
When a liquid flows through a collection of stationary obstacles, its flow can be smooth and laminar, or it can be swirling and turbulent. The liquid's flow is more likely to become turbulent if you increase its (A) speed or its density. (B) pressure. (C) speed or its viscosity. (D) viscosity or its density
(A) speed or its density. (greater density = more resistance against obstacles. Ex: water has little resistance to moving around a barrier, while pudding resists more)
A helium-filled balloon weighs only about 1/7th as much as the air it displaces. If you replace the helium gas in the balloon with hydrogen gas (which is half as dense as helium gas), the upward buoyant force on the balloon would (A) stay the same and the net force on the balloon would increase slightly in the upward direction. (B) increase and the net force on the balloon would increase slightly in the upward direction. (C) decrease and the net force on the balloon would roughly double in the upward direction. (D) increase and the net force on the balloon would roughly double in the upward direction.
(A) stay the same and the net force on the balloon would increase slightly in the upward direction.
A chandelier hangs motionless from the ceiling. The amount of momentum that chandelier is transferring to the ceiling each second is (A) the chandelier's weight times 1 second. (B) the chandelier's weight divided by the chandelier's mass. (C) zero. (D) the chandelier's mass times 1 second.
(A) the chandelier's weight times 1 second.
A candle is burning in a closed box that is perfectly insulated and isolated from the rest of the world. Because the candle is burning, (A) the entropy (disorder) of the box and its contents is increasing. (B) the energy of the box and its contents is decreasing. (C) the entropy (disorder) of the box and its contents is decreasing. (D) the energy of the box and its contents is increasing.
(A) the entropy (disorder) of the box and its contents is increasing.
You are dragging an old carpet across the floor in a straight line at a steady speed. Which of the following statements about the forces acting on the carpet is correct? (A) The amount of force that you're exerting on the carpet must be more than the amount of force that friction is exerting on it. (B) The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it. (C) The amount of force that you're exerting on the carpet must be more than the amount of its weight. (D) If you were to exert twice as much force on the carpet, it would slide across the floor twice as fast.
(B) The amount of force that you're exerting on the carpet must be equal to the amount of force that friction is exerting on it.
You drop an extremely bouncy rubber ball on a cement floor and it rebounds upward almost to its original height. Compare the ball's energy and momentum just before it bounced on the floor with its energy and momentum just after bounced off the floor. (A) The ball's energy and momentum changed only a little. (B) The ball's energy changed only a little, but its momentum changed significantly. (C) The ball's energy and momentum changed significantly. (D) The ball's energy changed significantly, but its momentum changed only a little.
(B) The ball's energy changed only a little, but its momentum changed significantly.
You forgot to tip the bartender who brought a Shirley Temple drink to your luxury hotel suite. So you're leaning out over the balcony of your 20th floor suite and dropping solid gold marbles into the tip jar on the ground floor patio bar. You notice that it takes 4 seconds for each marble to fall into the jar, 20 floors below. When each marble has fallen for only 2 seconds, which floor of the hotel is it nearest? [Note: neglect any effects due to the air.] (A) The marble is near the 10th floor. (B) The marble is near the 15th floor. (C) The marble is near the 8th floor. (D) The marble is near the 12th floor.
(B) The marble is near the 15th floor.
You drop a cylindrical can of soup and its flat bottom lands hard on the cement floor. As the result of the liquid-filled can's violent impact with the floor, its sides bulge outward. The bulge(s) is/are located at the (A) top of the can. (B) bottom of the can. (C) middle of the can. (D) top and bottom of the can, leaving the middle of the can unaffected.
(B) bottom of the can.
The hotter it is outside, the more electric energy an air conditioner must use to remove each joule of heat from the 72 °F indoor air in your home. It must consume more electric energy on a hotter day because (A) entropy flows into your home faster when the outdoor air is hotter. (B) delivering that joule of heat to the outdoor air creates less entropy as the outdoor air gets hotter. (C) delivering that joule of heat to the outdoor air creates more entropy as the outdoor air gets hotter. (D) heat flows into your home faster when the outdoor air is hotter.
(B) delivering that joule of heat to the outdoor air creates less entropy as the outdoor air gets hotter.
You watch from the ground as a crane lifts a large bucket of cement upward to a construction project. The bucket and cement are moving straight upward at constant velocity. As the crane's cable lifts the bucket, the cable is (A) not doing work on the bucket or the cement it contains. (B) doing work on the bucket and the bucket is doing work on the cement it contains. (C) doing work on the bucket, but the bucket is not doing work on the cement it contains. (D) not doing work on the bucket, but the bucket is doing work on the cement it contains.
(B) doing work on the bucket and the bucket is doing work on the cement it contains.
You're drinking a cup of hot coffee in an airplane at 35,000 feet. Suddenly the airplane pressurization system fails and the cabin's air pressure decreases abruptly. The coffee begins to boil because its temperature (A) has suddenly decreased. (B) hasn't changed but bubbles of pure steam are now stable inside it. (C) hasn't changed but the air bubbles inside it have suddenly expanded. (D) has suddenly increased.
(B) hasn't changed but bubbles of pure steam are now stable inside it.
On a cold morning, you seal your empty plastic water bottle and thus trap the air inside it. Later in the day, the bottle and its contents are much warmer and the elastic sides of the bottle are now stretched outward, so the bottle has slightly more volume than it had in the morning. Since the morning, the air pressure inside the bottle has (A) increased, but the density inside the bottle has stayed the same. (B) increased and the density inside the bottle has decreased. (C) stayed the same, but the density inside the bottle has decreased. (D) increased and the density inside the bottle has increased.
(B) increased and the density inside the bottle has decreased.
At high altitude, a commercial jetliner must compress the outside air before circulating it in the pressurized cabin. But the compressed air must first be sent through an air conditioner because the act of compressing air (A) increases the air's momentum. (B) increases the air's temperature. (C) turns it into a liquid and the air conditioner helps it evaporate back into a gas. (D) reduces the air's energy.
(B) increases the air's temperature.
On a hot, humid day, the liquid perspiration on your wet skin doesn't do a very good job of cooling you off. If the air were less humid but had the same temperature, you'd cool off better because water molecules would (A) leave your wet skin less often. (B) land on your wet skin less often. (C) land on your wet skin more often. (D) leave your wet skin more often.
(B) land on your wet skin less often.
Compared to a black iron woodstove, a woodstove made out of shiny gold would be (A) equally effective at heating a room because shiny gold and black iron are both dense materials. (B) less effective at heating a room because shiny gold does not radiate heat well. (C) equally effective at heating a room because shiny gold and black iron are both metals. (D) more effective at heating a room because shiny gold does not radiate heat well.
(B) less effective at heating a room because shiny gold does not radiate heat well.
You are competing in an archery contest and have just released an arrow toward the target. Neglect any effects due to the air. Once the arrow has left the bow and is heading forward toward the target, it experiences (A) a forward horizontal force until it reaches the midpoint of its trip to the target and then a backward horizontal force for the remainder of its trip. (B) no horizontal force in the forward direction. (C) a forward horizontal force that diminishes gradually as the arrow approaches the target. (D) a forward horizontal force that remains constant all the way to the target.
(B) no horizontal force in the forward direction.
When you strike a match on the side of the match box, you are using sliding friction to (A) push away the protective cap on the match to expose the thermal energy underneath. (B) provide the activation energy needed to initiate the chemical reactions of combustion. (C) melt the wax on the match and allow it to mix with the wood or paper. (D) wear away the protective cap on the match to expose the burning surface underneath.
(B) provide the activation energy needed to initiate the chemical reactions of combustion.
Modern double-pane windows provide excellent thermal insulation. The inner surface of one of those panes is coated with a transparent electrical conductor because that coating (A) prevents the argon gas atoms from transferring heat via conduction to the coated pane. (B) reflects infrared light and blocks radiative heat transfer from one pane to the other. (C) improves the thermal conductivity of the coated pane and helps keep it at the same temperature as the other pane. (D) attracts gas atoms and thereby limits convective heat transfer by the argon gas trapped between the panes.
(B) reflects infrared light and blocks radiative heat transfer from one pane to the other.
When a plane is flying through the air at 600 miles per hour, the air entering the inlet duct of its jet engine is traveling (A) faster than 600 miles per hour and its pressure is lower than atmospheric. (B) slower than 600 miles per hour and its pressure is higher than atmospheric. (C) slower than 600 miles per hour and its pressure is lower than atmospheric. (D) faster than 600 miles per hour and its pressure is higher than atmospheric.
(B) slower than 600 miles per hour and its pressure is higher than atmospheric.
You're at the lake and watch two children jump off a dock at the same time. They both kick equally hard during their jumps, but one child jumps mostly upward while the other child jumps mostly forward. After they leave the dock, (A) the two children reach the water at the same moment and but the child who jumps forward travels farther from the dock than does the other child. (B) the child who jumps forward reaches the water before the child who jumps upward. (C) the child who jumps upward reaches the water before the child who jumps forward. (D) the two children reach the water at the same moment and at the same distance from the dock.
(B) the child who jumps forward reaches the water before the child who jumps upward.
You're filming a movie and you arrange for two unoccupied cars to drive horizontally off a tall cliff side-by-side at the same velocity. The Mercedes sedan weighs twice as much as the Mini Cooper. In this situation, the two cars hit the level ground below the cliff at approximately (A) the same distance from the cliff, but the Mercedes sedan hits much sooner than the Mini Cooper. (B) the same time and at the same distance from the cliff. (C) the same time, but the Mercedes sedan hits considerably farther from the cliff than the Mini Cooper. (D) the same time, but the Mini Cooper hits considerably farther from the cliff than the Mercedes sedan.
(B) the same time and at the same distance from the cliff.
A huge abstract iron sculpture has been installed in front of the local art museum. It sits there motionless, "guarding" the main doorway. The sculpture is experiencing two forces: its weight downward and a force upward from the brick courtyard beneath it. We know that these two forces on the sculpture are equal in amount but oppositely directed because (A) Newton's third law requires that forces always appear in equal but oppositely directed pairs. (B) the sculpture is not accelerating, so the two forces must sum to zero. (C) for every action, there is an equal but oppositely directed reaction. (D) the sculpture has zero velocity.
(B) the sculpture is not accelerating, so the two forces must sum to zero.
A bottle in both thermal and phase equilibrium at 0 °C contains 1 kilogram of ice and 1 kilogram of liquid water. You move the bottle to a new location and allow it to reach equilibrium at -0.5 °C. The bottle now contains (A) 1.5 kilograms of ice and 0.5 kilograms of liquid water. (B) 0.5 kilograms of ice and 1.5 kilograms of liquid water. (C) 2 kilograms of ice. (D) 1 kilogram of ice and 1 kilogram of liquid water.
(C) 2 kilograms of ice.
You find three open mugs in the kitchen: one filled with boiling water at 212 °F (100 °C), the second filled with room temperature water at 68 °F (20 °C), and the third filled with very cold ice at 0 °F (-18 °C). Which of these mugs is releasing gaseous water molecules into the dry room air? (A) Only the room temperature water is releasing gaseous water molecules. (B) Only the boiling water and the room temperature water are releasing gaseous water molecules. (C) All three mugs are releasing gaseous water molecules. (D) Only the boiling water is releasing gaseous water molecules.
(C) All three mugs are releasing gaseous water molecules. (water's always releasing gaseous water molecules into the air)
You are paddling a canoe across a lake. You reach forward with your paddle, lower the paddle into the water, and then pull the paddle backward toward you. The paddle, canoe, and you all accelerate forward as you pull the paddle backward. What force causes the paddle, canoe, and you to accelerate forward? (A) The water exerts a buoyant force on the paddle, pushing the paddle in the forward direction. (B) The water exerts a lift force on the paddle, pushing the paddle in the forward direction. (C) The water exerts a drag force on the paddle, pushing the paddle in the forward direction. (D) The force of the paddle's momentum pushes it in the forward direction.
(C) The water exerts a drag force on the paddle, pushing the paddle in the forward direction.
Once a baseball leaves the pitcher's hand and is heading toward home plate, it gradually slows down. The primary reason for this slowing is that the air pressure (A) at the front and back of the ball is greater than atmospheric pressure, while the pressure on the sides of the ball is less than atmospheric. (B) at the front and back of the ball is less than atmospheric pressure, while the pressure on the sides of the ball is more than atmospheric. (C) at the front of the ball is greater than atmospheric pressure, while the pressure behind the ball is approximately atmospheric. (D) at the front of the ball is equal to atmospheric pressure, while the pressure behind the ball is less than atmospheric.
(C) at the front of the ball is greater than atmospheric pressure, while the pressure behind the ball is approximately atmospheric.
To save the earth from an asteroid impact years in the future, engineers land an explosive on the asteroid and blow it to bits. Just before the detonation, the asteroid was heading directly toward mars and just after detonation, the largest piece of asteroid is heading directly toward the sun. Just after the detonation, the total momentum of all the asteroid pieces points (A) directly toward the sun. (B) in a direction between the sun and mars. (C) directly toward mars. (D) directly away from mars.
(C) directly toward mars.
To catch a football successfully, you should allow the ball to push your hands in the direction of its travel. Allowing your hands to move with the football is crucial because it allows you to (A) add energy to the football. (B) extract momentum from the football. (C) extract energy from the football. (D) add momentum to the football.
(C) extract energy from the football.
If you kick a soccer ball straight forward at high speed with no spin at all, the air pressure at its surface will not be uniform. The location of the highest air pressure on the ball's surface will be at its (A) bottom. (B) top. (C) front (the side farthest from you). (D) back (the side nearest to you).
(C) front (the side farthest from you).
To win a stuffed animal at the state fair, you simply need to drop a glass marble onto a stationary glass plate and have the marble come to rest on that plate. Unfortunately, when the marble hits the plate, it bounces upward because the marble (A) transfers a large amount of momentum and energy to the plate. (B) retains essentially all of its momentum but transfers a large amount of energy to the plate. (C) retains essentially all of its energy but transfers a large amount of momentum to the plate. (D) retains essentially all of its energy and momentum.
(C) retains essentially all of its energy but transfers a large amount of momentum to the plate.
You are a famous stylist, putting the finishing touches on Lady Gaga's hair before her performance. Alas, your bottle of signature hair goo is almost empty! You put the cap on the bottle and swing it rapidly in a circle with its cap end pointing outward. The remaining hair goo collects just inside the cap and you are able to extract enough to complete your work. This technique works because (A) viscous forces push the hair goo toward the cap end of the bottle. (B) centrifugal force pushes the hair goo toward the cap end of the bottle. (C) the bottle's rapid inward acceleration leaves the hair goo behind so that it drifts toward the cap end of the bottle. (D) the force of the hair goo's momentum pushes it toward the cap end of the bottle.
(C) the bottle's rapid inward acceleration leaves the hair goo behind so that it drifts toward the cap end of the bottle.
Goose down is the soft, fluffy feathers near a goose's skin. The reason that a goose down jacket keeps you so warm in the winter is that (A) goose down's white coloring assists the radiative transfer of heat from the outer surface of the coat to your skin. (B) goose down's low average density reduces its buoyant force. (C) the fine structure of the goose down traps air and prevents it from undergoing convection. (D) the fibrous material in goose down is a poorer conductor of heat than the air it displaces.
(C) the fine structure of the goose down traps air and prevents it from undergoing convection.
Because of bad planning during the design and construction of a high-rise apartment building, all 50 floors of the building receive their water from a single pipe. That pipe is fed from a water tank located on the building's roof. On opening day, residents on various floors begin taking showers and have different experiences. They quickly discover that the total energy per liter in the spraying water is (neglecting any effects of viscosity and friction) (A) the same on all floors, but the speed of the spraying water is greater on higher floors. (B) smaller on higher floors (C) the same on all floors, but the speed of the spraying water is smaller on higher floors. (D) greater on higher floors.
(C) the same on all floors, but the speed of the spraying water is smaller on higher floors.
You are swinging a bucket full of water around you in a big horizontal circle at a constant speed. You are at the center of its circular path. The net force on the bucket points directly (A) downward. (B) away from you. (C) toward you. (D) along the bucket's velocity (along its direction of travel).
(C) toward you.
Ice cubes gradually shrink in a frost-free freezer because (A) the ice melts periodically and some of it evaporates before it can refreeze. (B) the freezer mice like to nibble on the ice cubes. (C) water molecules go directly from solid ice to gaseous water vapor. (D) the ice melts periodically and some of it drips into the bottom of the freezer.
(C) water molecules go directly from solid ice to gaseous water vapor.
You are riding a motorcycle at constant velocity along a horizontal road while wearing a heavy leather jacket. As you cruise down road, you are doing (A) (positive) work on the jacket and it is doing negative work on you. (B) (positive) work on the jacket and it is doing (positive) work on you. (C) zero work on the jacket and it is doing zero work on you. (D) negative work on the jacket and it is doing (positive) work on you.
(C) zero work on the jacket and it is doing zero work on you.
Firefighters are battling a fire on the 10th floor of an apartment building. When they stand on the ground, their fire hose can only shoot the steady stream of water up to the 8th floor. So they carry the end of the same fire hose up a 2-story-tall ladder and shoot water upward. The other end of the hose remains attached to the same water source as before. Now the steady stream of water rises to the (A) 9th floor. (B) 6th floor. (C) 10th floor. (D) 8th floor.
(D) 8th floor.
You and your friend carry identical water bottles from the first floor to the fifth floor. You start side-by-side and you finish side-by-side, but one of you uses the stairs while the other climbs straight up a ladder. Which of you did the most work on your water bottle? (A) The person who takes the most time to reach the fifth floor does the most work on the water bottle. (B) The person who uses the stairs does the most work on the water bottle. (C) The person who climbs the ladder does the most work on the water bottle. (D) Neither. You both do the same work on the water bottle.
(D) Neither. You both do the same work on the water bottle.
Two children are trying to lift toys using large helium balloons. One child is located in Norfolk, where the altitude is roughly sea level, and the other child is located in Denver, where the altitude is about 5,000 feet above sea level. Their balloons are identical in size and shape, and both locations have the same temperature and weather. Which balloon, if any, can lift more weight? (A) The Denver balloon can lift more weight. (B) The balloon with a picture of Dwayne Johnson on it can lift more weight, because he's so strong. (C) They can both lift equal weights. (D) The Norfolk balloon can lift more weight.
(D) The Norfolk balloon can lift more weight.
When you drop a beanbag on cement, the bag doesn't bounce. Suppose you are playing tennis with a beanbag instead of a tennis ball. How should you adjust your tennis racket to make the beanbag travel as fast as possible after you hit it with the racket? (A) You should tighten the strings so that the racket surface is like a firm trampoline. (B) You should replace the strings with a rigid carbon-fiber plate so that the racket surface acts like cement. (C) You should add mass to the racket so that it carries more momentum. (D) You should loosen the strings so that the racket surface is like a soft trampoline.
(D) You should loosen the strings so that the racket surface is like a soft trampoline.
To transform 1 kilogram of boiling-hot water at 100 °C into 1 kilogram of steam at 100 °C, you must (A) remove a large amount of heat to the water. (B) allow the water to boil for less than 5 minutes, although it doesn't require any additional heat. (C) allow the water to boil for more than 5 minutes, although it doesn't require any additional heat. (D) add a large amount of heat to the water.
(D) add a large amount of heat to the water.
You are standing in a cable car that is moving up the side of a mountain at a constant velocity. The force that the cable car is exerting on you points (A) horizontally forward, toward the mountain itself. (B) down and forward, at right angles to the cable itself. (C) up and forward, in the direction of the cable itself. (D) directly upward.
(D) directly upward.
A satellite is traveling around the earth in a circular orbit. It briefly fires its rocket engine to increase its speed in the forward direction; it is suddenly going faster but its direction of travel didn't change. As a result of this speed increase, the orbiting satellite's average distance from the center of the earth (A) remains unchanged, but the orbit is no longer circular. (B) remains unchanged and the orbit continues to be circular. (C) decreases. (D) increases
(D) increases
When wood burns in air, the water and carbon dioxide molecules that form as the result of combustion reactions have (A) more chemical potential energy than the original wood and air molecules (B) more chemical momentum than the original wood and air molecules (C) less chemical momentum than the original wood and air molecules (D) less chemical potential energy than the original wood and air molecules
(D) less chemical potential energy than the original wood and air molecules
The living room is cold, so your friend brings in an electric hotplate to warm the air. To make sure that no one touches the red-hot surface of that hotplate, your friend places the hotplate on a high ledge near the ceiling. Heat will flow from the hotplate to people sitting near the floor (A) primarily via convection and radiation, with almost no heat flowing via conduction. (B) equally poorly via conduction, convection, and radiation, and the room will remain cold. (C) equally well via conduction, convection, and radiation, and the room will become warm. (D) primarily via radiation, with almost no heat flowing via conduction or convection.
(D) primarily via radiation, with almost no heat flowing via conduction or convection.
An airplane cruises at constant velocity into a region of calm, motionless air. After the plane has passed through that region of air, the air's total momentum is (A) still zero, but the air may be turbulent (contain swirls and vortices). (B) downward and forward (in the direction of the airplane's motion). (C) downward and backward (in the direction opposite the airplane's motion). (D) straight downward.
(D) straight downward.
You are filling a large plastic bag with helium. At first, the bag doesn't float. But as you keep inflating the bag with helium, it eventually begins floating because (A) the helium-filled bag's weight decreases as you put more lightweight helium particles inside it and eventually it becomes weightless. (B) the average pressure of the helium-filled bag increases as it fills and its pressure eventually becomes greater than that of the air it displaces. (C) the upward buoyant force on a bag full of helium is larger than the buoyant force on an identical bag full of air. (D) the average density of the helium-filled bag decreases as it fills and its density eventually becomes less than that of the air it displaces.
(D) the average density of the helium-filled bag decreases as it fills and its density eventually becomes less than that of the air it displaces.