The timekeeper of quartz clock is a tiny quartz tuning fork. Suppose that the clock is running a little slow (i.e., it is counting off the seconds more slowly than it should). What change to the tuning fork could fix this problem, so that the clock keeps correct time?

One of the components of an air conditioner is its evaporator. Inside that evaporator, the unit's working fluid transforms from a liquid to a gas. While this transformation is occurring, what else is happening around the evaporator?

A window air conditioner normally operates between the indoor air and the outdoor air. Suppose you place the unit on a table in the middle of the room, plug it in, and turn it on. What will happen to the average temperature of the room as the unit operates?

A spaceship in deep empty space is moving toward a remote space station at a constant velocity. To maintain that constant velocity, what forward thrust (forward propulsive force) must the spaceship's rocket engine obtain from its plume of exhaust?

You are standing in front of an open freezer at the grocery store, trying to decide which flavor of ice cream to buy. Even though you aren't touching the freezer or the cold air pouring out of it toward the floor, you still feel surprisingly cold. Why is the freezer making you feel cold?

After a storm covers the ground with snow, the weather turns warm and the snow begins to melt. You are in a restaurant, with a glass of ice and water in front of you. The temperature outside is 50 °F (10 °C) and the temperature inside is 68 °F (20 °C). Compare the temperature of the melting snow outside to the ice water in your glass inside.

A gong is a stiff metal disk that emits sound when struck by a mallet. The pitch of the gong's fundamental vibrational mode is present in its sound and that pitch doesn't change as the gong's loudness decreases. The gong's other tones, however, give it a brash sound similar to that of a drum or cymbal rather than the more melodic sound a string or wind instrument. That's because the gong is a vibrating surface and it

You are at the seashore, watching a seabird float on the water far from shore. As a large wave travels across the water toward shore, it encounters the bird. What effect does the passing wave have on the bird?

You are riding a cable car in San Francisco and are moving uphill at constant velocity. What overall force is the cable car exerting on you? [Neglect any effects due to the air.]

What is the primary reason why increasing the concentration of carbon dioxide in the Earth's atmosphere leads to an increase in the average temperature near the Earth's surface?

In January 1903, Wilbur Wright made a discovery that revolutionized airplane propellers and made powered flight possible. His realization was that each blade of a propeller is

The three nonflammable objects in your hand 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 high temperature: 1800 °C. They remain solid. Which one is glowing most brightly with visible light?

You are pulling a wagon forward on a level sidewalk and the wagon is experiencing no other horizontal force. As you exert your forward force on the wagon, the wagon exerts a backward force on you. When do those two forces cancel so that the wagon does not accelerate?

Why does water boil at a lower temperature in the Rocky Mountains than it does in Charlottesville?

A yardstick (or meter-stick) is a long metal rectangle of uniform thickness. When the yardstick is vibrating in is fundamental vibrational mode, it bows in alternating directions along its length (see image) with a frequency of 2 Hz (2 cycles per second). If you cut the yardstick in half along its length (see image), the fundamental vibrational mode of each half-yardstick will have what frequency?

An airplane in flight gradually turns toward the right. What force does it use to change its velocity toward the right?

When you play in water waves at the seashore, you can often outrun those wave. Tsunamis, the giant water waves created by earthquakes and other cataclysmic events, travel at race-car speeds across the ocean. Why do these waves have such different speeds?

A toy electric train is traveling around a circular toy track at a constant speed. In which direction is the train accelerating?

A squirrel runs past and two dogs simultaneously leap horizontally off the porch to give chase. The tan dog weighs twice as much as the red dog, but the red dog's horizontal starting velocity was twice that of the tan dog. When the dogs land on the level ground below the porch,

On a hot summer day, your home's air conditioner is maintaining the indoor air temperature at 72 °F. If the hot outdoor air becomes even hotter, how will that temperature increase affect the amount of electric energy the air conditioner consumes while pumping 1 joule of heat from the indoor air to the outdoor air?

You are pulling a toboggan (a snow sled) full of friend forward across level snow. The toboggan is traveling at a constant horizontal velocity. Compare the forward force you exert on the toboggan to the backward force the snow exerts on the toboggan.

When a ray of sunlight passes through an otherwise darkened room, it illuminates tiny dust particles in the air. If the room's air were perfectly calm, no wind at all, the dust particles would

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

An acoustic guitar has an elaborately shaped wooden box in addition to its strings. What is the primary purpose of that box?

Why must an automobile engine (an internal combustion engine that burns gasoline) release a large amount of thermal energy into the environment, rather than converting all of that thermal energy into work?

A spare bicycle wheel accidently falls off a shelf and rolls all the way across the warehouse before finally falling over. That wheel cannot remain upright when it is stationary, so why does it stay upright so long when it is rolling?

The timekeeping pendulum of a grandfather clock has been adjusted so that the clock keeps perfect time here in Charlottesville. If that clock is moved carefully to top of the Blue Ridge Mountains, how will the clock behave?

During the power stroke of an internal combustion engine, the hot burned gas pushes the piston out of the cylinder. What are happening to the pressure, density, and temperature of the burned gas during the power stroke?

You are visiting a playground with a variety of swings and other toys. 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 oscillation than the boy because

A microwave oven can heat water in a glass container to a temperature several degree above water's normal boiling temperature. That water is superheated (or overheated). How can this superheating occur?

When wood burns in air, the water and carbon dioxide molecules that form as the result of combustion reactions have

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 ordered energy per liter in the spraying water is (neglecting any effects of viscosity and friction)

You are designing a chair for a museum. While your chair will be a work of art, it must also be practical and it mustn't tip over easily. To ensure that it stays upright, you design it so that its

When water flowing steadily through a garden hose flows around a bend in that hose, its pressure changes. The water pressure

A lighter person and a heavier person bungee-jump simultaneously from a bridge, side by side. They are attached to the level bridge by identical elastic cords. After a few thrilling seconds, they are both bouncing gently up and down. Which of the following correctly describes the periods of their bouncing motions and their equilibrium heights (altitudes) above the ground?

You are camping in the wilderness on a bitter cold day and you want to insulate your tent as effectively as possible. All you have on hand are two huge containers of popcorn, one full of popped corn and one full of unpopped corn. The corn kernels are all chemically identical, but the popped corn kernels are filled with tiny air bubbles. Which corn should you surround yourself with inside the tent to experience the best thermal insulation?

Your home's climate-control system has carefully adjusted the indoor air's temperature and humidity so that they differ from those of the outdoor air. A visitor enters and leaves the front door of your home open. What happens to the entropy of the universe because of having the door open?

As you observe the Atlantic Ocean from a beach in eastern Virginia, you notice that the water's average level varies up and down rhythmically with about a 12-hour cycle: from high tide (maximum height) to low tide (minimum height) and back to high tide. What is the primarily cause of this cycle of tides?

A building is being demolished and the workers are using two wrecking balls to do the job. Those wrecking balls are giant pendulums hanging from tall cranes and they're identical except that one ball is twice as heavy as the other. The balls are pulled away from equilibrium equal distances and then released from rest. They swing through equilibrium and collide violently with the building's wall. Compare their momentums, velocities, and kinetic energies as they swing through equilibrium.

If you reach into steam (gaseous water) at a temperature of 212 °F (100 °C), your skin heats up much more quickly than if you reach into air at a temperature of 212 °F (100 °C). Why?

Two glass bottles, one blue and one green, contain only liquid water and water vapor. The liquid and gas are in phase equilibrium, but the water vapor in the blue bottle has a significantly lower density than the water vapor in the green bottle. What else is different about the two bottles?

If you blow across the top of a half-full bottle of water, you can produce a clear tone. If you drink some of the water and try this again, the frequency of the sound produced will

You are preparing to plant some seeds in a flowerpot. You have a clay pot, some dry soil, and a pitcher of cold water. Which of the following actions would increase the total entropy of these 3 items: combining the water and soil, heating the water to room temperature, and/or accidently breaking the clay pot?

During the winter, your home is heated by a heat pump. When the heat pump is consuming 1000 watts of electric power, how much thermal power is it delivering to the air in your home?

Your coffee has cooled off and you decide to heat it the hard way: you stir the coffee vigorously for 10 minutes. The coffee does become slightly hotter. What causes this rise in temperature?

How does ice form on the freezing compartment of a simple refrigerator (a typical dorm refrigerator), even when all you do is open and close the refrigerator door occasionally?

A soccer ball that is moving forward through calm air experiences the backward force of pressure drag. Doubling the ball's forward velocity would have what effect on that pressure drag force? [Assume no change in the cross sectional area of the ball's turbulent wake.]

An airplane is in level flight. The air stream that encounters the underside of the airplane's wing bends downward, away from the wing's bottom surface. How do the pressure and speed of the air near the wing's bottom surface compare to their values far from the wing?

The fundamental vibrational mode of a violin's A string has a frequency of 440 Hz (440 cycles per second). When you pluck that string with your finger, the vibrating string can cause the violin to produce sounds with which frequencies?

Two metal cooking pots are identical except that one is made of aluminum and one is made of stainless steel. Why does the aluminum pot provide more uniform cooking when placed on a stovetop burner than does the stainless steel pot?

When you push your warm hand against a cold, immovable granite wall, what energy does your hand transfer to that wall?

A diesel engine has no sparkplugs. What provides the high temperatures needed to ignite the fuel in a diesel engine?

You throw a tennis ball to friend located on the other side of a level field. When the ball is at peak height, about half way across the field, what forward force is the ball experiencing? [Neglect effects due to the air.]

You are riding a roller coaster with a loop-the-loop and are currently upside-down at the top of the loop. You are pressed tightly into your seat, even though that seat is above you (as viewed by a person on the ground). Which of the following correctly describes your motion?

Sunlight carries heat from the Sun to the Earth. The Sun's surface temperature is about 6000 K and the Earth's surface temperature is about 300 K. A solar cell exposed to sunlight provides electric energy, an ordered form of energy. What is the maximum fraction of sunlight's thermal energy that a solar cell can convert continuously into electric energy?

A car has driven off the road into a snowdrift and you are trying to pull the car out. You tie one sleeve of an old sweater to your car and the other sleeve of the sweater to the stuck car. As you drive forward, the sweater stretches and breaks. The stuck car never moved at all. Stretching and breaking the sweater took energy, but where did that energy come from?

You are looking at two different photographs of the same perfectly isolated system. Each photo shows a room with a small plastic bucket on the floor. In one photo, the bucket is full of water and the room air is dry. In the other photo, the bucket is empty and the room air is moist. Compare those two situations.

You are pushing a child on a swing. You exert a forward force of 10 newtons on the child as the child moves away from you. The child exerts a backward force on you of

To win a prize at the fair, you must toss a basketball into a rigid fruit basket and have the ball remain in that basket. The basket is tipped toward you and nailed immovably to the wall. Its lower lip has just enough uphill slope to keep a stationary ball from rolling out. Each time you throw the ball into the basket, the ball bounces and rolls onto the floor. The conserved quantity that the basketball is unable to get rid of in order to stay in the basket is

You are eating outside on a hot summer day and an ice cube in your glass of ice water is gradually disappearing. Which of the following describes the situation near the surface of that ice?