Problem 1:
A chandelier hangs motionless from the ceiling. The amount of momentum that chandelier is transferring to the ceiling each second is
Answer: (A) the chandelier's weight times 1 second. [75.0% picked]
Why: 
Video Discussion
Problem 2:
When you strike a match on the side of the match box, you are using sliding friction to
Answer: (B) provide the activation energy needed to initiate the chemical reactions of combustion. [98.7% picked]
Why: Video Discussion
Problem 3:
A satellite is orbiting the earth in a not-quite-circular orbit. As it moves, the satellite is accelerating
Answer: (A) directly toward the center of the earth. [81.8% picked]
Why: Video Discussion
Problem 4:
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.]
Answer: (B) The marble is near the 15th floor. [69.9% picked]
Why: Video Discussion
Problem 5:
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
Answer: (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. [80.1% picked]
Why: Video Discussion
Problem 6:
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
Answer: (A) stay the same and the net force on the balloon would increase slightly in the upward direction. [33.1% picked]
Why: Video Discussion
Problem 7:
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
Answer: (A) does not flow at all. [93.2% picked]
Why: Video Discussion
Problem 8:
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
Answer: (B) the sculpture is not accelerating, so the two forces must sum to zero. [42.4% picked]
Why: Video Discussion
Problem 9:
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
Answer: (D) increases. [66.5% picked]
Why: Video Discussion
Problem 10:
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
Answer: (A) have slowed the water flow through hose and plumbing so that the water wastes less energy doing working against viscous forces. [44.5% picked]
Why: Video Discussion
Problem 11:
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
Answer: (A) decreasing, the entropy of outdoor air is increasing, and the total entropy of both is increasing. [64.0% picked]
Why: Video Discussion
Problem 12:
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?
Answer: (D) You should loosen the strings so that the racket surface is like a soft trampoline. [85.6% picked]
Why: Video Discussion
Problem 13:
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)
Answer: (C) the same on all floors, but the speed of the spraying water is smaller on higher floors. [50.4% picked]
Why: Video Discussion
Problem 14:
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?
Answer: (D) The Norfolk balloon can lift more weight. [57.6% picked]
Why: Video Discussion
Problem 15:
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
Answer: (B) increased and the density inside the bottle has decreased. [64.8% picked]
Why: Video Discussion
Problem 16:
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
Answer: (C) at the front of the ball is greater than atmospheric pressure, while the pressure behind the ball is approximately atmospheric. [44.1% picked]
Why: Video Discussion
Problem 17:
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?
Answer: (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. [96.2% picked]
Why: Video Discussion
Problem 18:
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
Answer: (A) less than atmospheric pressure and the average air pressure just below its wings is more than atmospheric pressure. [68.6% picked]
Why: Video Discussion
Problem 19:
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
Answer: (A) increase in the density of the air inside the ball. [55.9% picked]
Why: Video Discussion
Problem 20:
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
Answer: (C) the fine structure of the goose down traps air and prevents it from undergoing convection. [94.1% picked]
Why: Video Discussion
Problem 21:
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
Answer: (A) speed or its density. [50.0% picked]
Why: Video Discussion
Problem 22:
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
Answer: (A) condenses on the colder vegetables and releases a large amount of heat to the vegetables. [94.1% picked]
Why: Video Discussion
Problem 23:
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
Answer: (B) doing work on the bucket and the bucket is doing work on the cement it contains. [58.5% picked]
Why: Video Discussion
Problem 24:
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
Answer: (C) zero work on the jacket and it is doing zero work on you. [81.8% picked]
Why: Video Discussion
Problem 25:
Compared to a black iron woodstove, a woodstove made out of shiny gold would be
Answer: (B) less effective at heating a room because shiny gold does not radiate heat well. [96.6% picked]
Why: Video Discussion
Problem 26:
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
Answer: (D) primarily via radiation, with almost no heat flowing via conduction or convection. [51.3% picked]
Why: Video Discussion
Problem 27:
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
Answer: (D) straight downward. [41.1% picked]
Why: Video Discussion
Problem 28:
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
Answer: (C) retains essentially all of its energy but transfers a large amount of momentum to the plate. [92.8% picked]
Why: Video Discussion
Problem 29:
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
Answer: (B) increases the air's temperature. [89.4% picked]
Why: Video Discussion
Problem 30:
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?
Answer: (D) Neither. You both do the same work on the water bottle. [94.9% picked]
Why: Video Discussion
Problem 31:
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
Answer: (B) the same time and at the same distance from the cliff. [84.3% picked]
Why: Video Discussion
Problem 32:
Ice cubes gradually shrink in a frost-free freezer because
Answer: (C) water molecules go directly from solid ice to gaseous water vapor. [74.2% picked]
Why: Video Discussion
Problem 33:
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
Answer: (B) delivering that joule of heat to the outdoor air creates less entropy as the outdoor air gets hotter. [39.8% picked]
Why: Video Discussion
Problem 34:
When wood burns in air, the water and carbon dioxide molecules that form as the result of combustion reactions have
Answer: (D) less chemical potential energy than the original wood and air molecules [77.1% picked]
Why: Video Discussion
Problem 35:
To transform 1 kilogram of boiling-hot water at 100 °C into 1 kilogram of steam at 100 °C, you must
Answer: (D) add a large amount of heat to the water. [67.8% picked]
Why: Video Discussion
Problem 36:
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
Answer: (D) directly upward. [91.1% picked]
Why: Video Discussion
Problem 37:
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
Answer: (B) no horizontal force in the forward direction. [93.2% picked]
Why: Video Discussion
Problem 38:
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
Answer: (A) it is deflecting the airflow around it toward your left. [73.7% picked]
Why: Video Discussion
Problem 39:
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
Answer: (C) toward you. [75.4% picked]
Why: Video Discussion
Problem 40:
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
Answer: (B) reflects infrared light and blocks radiative heat transfer from one pane to the other. [39.0% picked]
Why: Video Discussion
Problem 41:
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
Answer: (C) directly toward mars. [52.5% picked]
Why: Video Discussion
Problem 42:
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
Answer: (C) the bottle's rapid inward acceleration leaves the hair goo behind so that it drifts toward the cap end of the bottle. [81.8% picked]
Why: Video Discussion
Problem 43:
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.
Answer: (B) The ball's energy changed only a little, but its momentum changed significantly. [91.9% picked]
Why: Video Discussion
Problem 44:
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
Answer: (A) helping you retain a thin layer of warm air near your skin. [62.7% picked]
Why: Video Discussion
Problem 45:
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?
Answer: (A) The object that original appeared black. [96.2% picked]
Why: Video Discussion
Problem 46:
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,
Answer: (B) the child who jumps forward reaches the water before the child who jumps upward. [76.3% picked]
Why: Video Discussion
Problem 47:
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
Answer: (B) land on your wet skin less often. [19.5% picked]
Why: Video Discussion
Problem 48:
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?
Answer: (C) The water exerts a drag force on the paddle, pushing the paddle in the forward direction. [53.8% picked]
Why: Video Discussion
Problem 49:
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
Answer: (D) 8th floor. [81.8% picked]
Why: Video Discussion
Problem 50:
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
Answer: (C) extract energy from the football. [61.9% picked]
Why: Video Discussion
Problem 51:
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)?
Answer: (A) The room containing moist air and an empty bowl has the greater entropy. [61.4% picked]
Why: Video Discussion
Problem 52:
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
Answer: (C) 2 kilograms of ice. [46.2% picked]
Why: Video Discussion
Problem 53:
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
Answer: (B) bottom of the can. [58.1% picked]
Why: Video Discussion
Problem 54:
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?
Answer: (A) You do work as you stir the water and that work becomes thermal energy in the turbulent liquid. [89.4% picked]
Why: Video Discussion
Problem 55:
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
Answer: (B) hasn't changed but bubbles of pure steam are now stable inside it. [55.9% picked]
Why: Video Discussion
Problem 56:
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
Answer: (C) front (the side farthest from you). [83.9% picked]
Why: Video Discussion
Problem 57:
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,
Answer: (A) the entropy (disorder) of the box and its contents is increasing. [94.5% picked]
Why: Video Discussion
Problem 58:
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?
Answer: (C) All three mugs are releasing gaseous water molecules. [84.7% picked]
Why: Video Discussion
Problem 59:
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.
Answer: (A) Water on the left side has lower pressure and higher speed than water on the right side. [59.3% picked]
Why: Video Discussion
Problem 60:
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
Answer: (B) slower than 600 miles per hour and its pressure is higher than atmospheric. [53.4% picked]
Why: Video Discussion