Two balls, one of which weighs twice as much as the other, roll off of a horizontal table together at the same initial velocity. In this situation,

A car drives over a fire hydrant and breaks it off at ground level. A fountain of water rises upward into the open air. As that rising water's gravitational potential energy increases,

The air in a steam room is hotter than body temperature and it is at 100% relative humidity. If you wave your arms in the steam room, water will

Your new food-storage cooler is perfectly insulated: no heat can flow into it or out of it. You open the cooler and place a small dish of water in the cooler's warm dry air. You close the cooler. A few hours later, the cooler is full of cool moist air and the dish is empty. The cooler's overall entropy

After clearing the bar in the high jump, you land softly on a giant mattress. Landing on the mattress is much more comfortable than landing on a sand heap of equal size because you transfer

A sealed bottle of perfume is sitting on a dresser in a thermally isolated room. A spring pops the lid off the perfume bottle and the air in the room gradually acquires a beautiful scent. While the room air is developing its scent, the total entropy in the thermally isolated room is

Your winter jacket contains 8 ounces of goose down insulation, just enough to completely fill the interior of the jacket. Suppose you open the seams and tightly pack 8 more ounces of goose down insulation into the jacket. After sewing up the seams, your jacket will be

Since a water molecule weighs less than the average air molecule, humid air is less dense than dry air. Suppose that the humidity of the air increases significantly during an orchestra concert. How will the resulting decrease in air density affect the wind instruments (e.g., flutes, clarinets, oboes)?

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 satellite is orbiting the earth in a circular orbit. It is high above the atmosphere. As it moves, the satellite is accelerating

You are holding three nonflammable objects. They are identical except that one is black, one is white, and one is shiny. You place them in a roaring fire and soon they have the same temperature: 1800 °C. They remain solid. Which one is glowing most brightly?

You can add a thickening agent to soup to make that soup much more viscous without changing its density. You are stirring two pots of soup, one without the thickener and one with the thickener, using identical spoons. You find that

You are visiting a playground and you notice that a girl on one swing completes each full cycle of motion in much less time than a boy on another swing. The girl has a much shorter period of motion (time to complete one full cycle) than the boy because

The temperature of the air in a concert hall is increasing although its pressure is not. As a result of this temperature rise, the hall's pipe organ

As you sit in a restaurant, you tap your wineglass with your fork and it emits a loud tone. A wineglass elsewhere on the table starts to vibrate even though you never touched it directly. The pitch emitted by the second wineglass is

When water rushing through a fire hose flows around a bend in that hose, its pressure changes. The water pressure

You are standing in the middle of a bus that is moving forward on a level road at constant velocity. Suddenly, another passenger accidentally spills an enormous container of salad oil and the floor becomes perfectly slippery. It cannot exert any frictional forces on your feet. Because nothing else is touching you, you

A typical heat pump (an air conditioner run backwards so that it heats the indoor air) consumes 1000 watts of electric power. How much thermal power does it deliver to the indoor air?

A hot air balloon is passing over your head when the pilot turns on the flame and heats up the air inside the balloon's envelope (the balloon's fabric skin). That envelope is open at the bottom, where the flame heats it. As the temperature of the air inside the unsealed envelope increases, the

During the power stroke in one cylinder of a car's engine, the burned fuel and air push the piston out of the cylinder. In accordance with Newton's third law, the piston pushes back on the burned gas. Overall, the

If you tape coins to the two tines (arms) of a tuning fork, the frequency (or pitch) of that tuning fork will

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 bottle in thermal equilibrium at 0 °C (32 °F) contains 1 kilogram of ice and 1 kilogram of liquid water. You move the bottle to a new location and allow it to reach thermal equilibrium at +0.5 °C. The bottle now contains

When you light a natural gas stove, its flame turns natural gas molecules and oxygen into water and carbon dioxide molecules. The molecules that form during this combustion have

The E string of a violin has a fundamental frequency of 660 Hz (660 cycles-per-second). If you cause that string to vibrate as three one-third strings, its loudness

You are a photographer, capturing images of divers as they plummet 20 meters (66 feet) to the ocean beneath a cliff. It takes each diver 2 seconds to fall from the cliff to the water and you want to photograph each diver after 1 second of falling. How far above the water should you aim your camera?

It's a warm summer day and you and your friends are drinking root beers on the lawn outside your dorm. You decide to move the refrigerator out of the air-conditioned dorm and onto the lawn. As the result of this move, the refrigerator consumes more electric power because

You are using a hand-powered pump to add air to a bicycle tire. As you pump air quickly into the tire,

You are working at an art supply company in northern Siberia when a blizzard traps you in the unheated warehouse overnight. You are freezing and can't find a blanket anywhere. Instead, you find rolls of various materials: (a) thin, dense black paper, (b) thick, low-density black paper, (c) clear plastic sheeting, and (d) aluminum foil. To keep warmest, which pair of materials should you surround yourself with?

You are taking a self-defense class and are learning to get a heavy hanging bag swinging back and forth by hitting it at the proper moments during its swing. To make the bag swing further, you should punch it away from you every time it is

When water flows through a nozzle, the water's pressure

You are already in the shower when you discover your tube of shampoo is almost empty. To get the last few drops of shampoo, you swing the tube rapidly in a circle with the cap-end of the tube pointing away from you. This technique works because

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)

You take some very cold ice cubes out of the freezer and place them on the warm granite countertop. The ice cubes begin to make noises: they creak, groan, and even crack. Sound carries ordered energy, yet the ice cubes and granite countertop started with only thermal energy. Why did the sound only appear when the ice cubes touched the granite countertop?

You are an astronaut floating in empty space far from Earth or anything else. You throw a video camera forward as hard as you can. While that camera is moving forward at great speed, the net force on that camera is

You are inflating a shiny plastic balloon with helium. The balloon starts as a thin, flat bag but it gradually gets thicker as it fills. At first, the thin plastic balloon doesn't float. But as you keep adding helium to the balloon and it gets thicker, it eventually begins floating because

You stretch a rope between two trees to serve as a clothesline. After plucking the rope by accident, you notice that it is vibrating slightly in its fundamental vibrational mode and that its period (time to complete 1 full cycle of motion) of 1 second. What could you do to the rope to increase (lengthen) that period?

You drop a cylindrical can of tomato sauce 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

If you're designing an energy efficient automobile, why should you minimize the diameter of the turbulent wake it leaves behind in the air?

Even though your Thanksgiving dinner consists of a tofu turkey, you discover that it contains a wishbone. Who knew? You and your cousin decide to break the wishbone; the one with the large piece gets their wish. Your cousin holds one end of the wishbone motionless as you pull the other end toward you rapidly. The wishbone snaps and you're left holding only a tiny fragment. Better luck next time! Breaking the wishbone required energy and that energy was provided by

The first kind of perpetual motion machine provides an inexhaustible supply of mechanical work (or the equivalent of work), but consumes nothing at all from its environment, not even heat. An example would be a black box that consumes nothing yet provides electricity forever. This form of perpetual motion machine is impossible because it

An automobile engine "knocks" when the gas in its cylinder ignites spontaneously rather than waiting for the sparkplug to ignite it. During which of the 4 strokes can this premature ignition occur?

The second kind of perpetual motion machine provides an inexhaustible supply of mechanical work (or the equivalent of work), but consumes only heat from its constant-temperature environment. An example would be a black box that absorbs heat from the 70 °F room air and converts that heat into electricity forever. This form of perpetual motion machine is impossible because it

A rubber duck is floating motionless on the water in a bathtub and the top of the duck is exactly 4 inches above the water level. You pour a thin layer of bath oil onto the water. The top of the duck is now

The hotter the outdoor air, the more electric energy an air conditioner must use to remove each joule of heat from the 72 °F indoor air in your home. The air conditioner must consume more electric energy on a hotter day because

You are flying a kite on a long string and the kite hovers motionless in the sky as the wind blows past it. The kite is high up to your east and you are pulling the kite string downward and westward. In which direction is the kite pushing on the air that passes it?

If you heat water in a glass container in the microwave oven for a long time and notice that it isn't boiling during the last few seconds of cooking, you would be wise to

An airplane is cruising at constant velocity, 35,000 feet in the air. Which of the following correctly describes the situation above the airplane's wing?

As it flies horizontally over the net, a volleyball experiences pressure drag because the air pressure

When you leave dry ice (solid carbon dioxide) on the kitchen counter, it gradually disappears without ever becoming liquid. If you were to examine the surface of the dry ice closely, you'd find that carbon dioxide molecules

An automobile's internal combustion engine burns a mixture of fuel and air in its cylinders. It is impossible for this engine to convert all of the chemical potential energy of the fuel and air mixture into mechanical work because burning that mixture increases its

You are washing your car by spraying water at it from a hose and nozzle. At the center of the stream of water, right where it hits the car, the water is coming to a complete stop. The pressure in the water at the center of the stream as it touches the car is

If you hold a full glass bottle of root beer in your hand and pound the top of that bottle with a rubber mallet,

Most electric power generating stations use steam to generate electricity. These stations all have cooling towers or other devices for getting rid of waste heat. There is no way to operate a steam-powered generating station without sending waste heat into the environment because

You are fond of boiled eggs, which you normally cook for 3 minutes while in Charlottesville. You are casually hiking on Mt. Everest, 29,000 feet above sea level, and stop for a snack. You put an egg in a pot of boiling water and wait 3 minutes. Sadly, the egg turns out badly undercooked because the reduced atmospheric pressure in the mountains

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 it bounced off the floor.

On a humid summer day, perspiration doesn't cool you off much because

If you ever get caught in a forest fire, you should try to prevent the fire from transferring heat to you. One possible approach is to find a patch of bare unburnable ground that is as low as possible and lie on that ground. That will nearly eliminate heat transfer to you via

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

On a cold winter day, you partially fill a Ziploc plastic bag with warm indoor air, seal it, and set it outside to cool off. A few minutes later, you notice that the bag seems to have deflated somewhat. The temperature of the air inside the bag has decreased, resulting in a significant