Physics 4.0

1.

1 point

Use the concept of convection to explain why firewood burns better when it’s raised above the bottom of a fireplace on a grate.

Raising the wood allows to convection cause air to circulate around the wood, giving it more oxygen.

Convection pulls in cooler air to the bottom.

Raising the wood allows convection to carry away the heat better.

Convection causes warmer air to rise.

2.

1 point

Explain how convection contributes to the shape of a candle flame.

The flame radiates heat upward.

The rising warm air causes the flame to elongate upward.

The warm air rises.

Cooler air comes in at the bottom.

3.

1 point

Frozen vegetables will “freeze-dry” if they’re left in cold, dry air. How can water molecules leave the frozen vegetables?

They melt away.

They evaporate into the surrounding air.

They dissolve into the food.

They sublime into the surrounding air.

4.

1 point

You’re floating outside the space station when your fellow astronaut tosses you a cold bottle of mineral water. It’s outside your space suit but you open it anyway. It immediately begins to boil. Why?

There is nothing to keep the water in liquid form.

Nature abhors a vaccum, so the water boils.

The boling point of water is much lower at very low pressure.

Liquids always boil at zero pressure.

5.

1 point

If you open the door of your refrigerator with the hope of cooling your room, you will find that the room’s temperature actually increases somewhat. Why doesn’t the refrigerator remove heat from the room?

The refrigerator releases more energy as heat than it removes from the air inside itself.

The refrigerator does remove heat from the room.

The refrigerator transfers heat from outside itself to inside itself.

To remove energy from the room would require an air conditioner, not a refrigerator.

6.

1 point

The space shuttle generates thermal energy during its operation in earth orbit. How is it able to get rid of that thermal energy as heat in an airless environment?

The heat leaves the shuttle as thermal radiation.

The heat is conducted off by the vacuum

The heat is convected off by the vacuum.

The heat leaves the shuttle as thermal energy.

7.

0 points

What is one word you would use to describe this class? If you want to write more feel free.

8.

1 point

An icy sidewalk gradually loses its ice even when the weather stays cold. Where does the ice go?

It sublimes into the air.

It evaporates into the air.

The sun melts it.

Putting salt on the sidewalk will cause the ice to melt.

9.

1 point

When you throw a hot rock into a cold puddle, what happens to the overall entropy of the system?

It decreases.

It remains constant.

More information is needed

It increases.

10.

1 point

Why do aluminum pans heat food much more evenly than stainless steel pans when you cook on a stove?

Aluminum has a much lower latent heat of fusion than stainless steel.

Aluminum has a much lower specific heat than stainless steel.

Aluminum has a much higher thermal conductivity than stainless steel.

Aluminum has a much higher specific heat than stainless steel.

11.

1 point

A high-flying airplane must compress the cold, rarefied outside air before delivering it to the cabin. Why must this air be air-conditioned after the compression?

The outside air becomes hot during the compression.

Air conditioning removes excess moisture from the outside air.

The outside air would not need to be air conditioned if it were not so thin.

Ths is reverse air-conditioning and raises the temperature of the cold outside air to cabin temperature.

12.

1 point

When you put a loaf of bread in a plastic bag, there is still air around the bread. Why doesn’t the bread dry out as quickly in the bag as it does when there’s no bag around it?

The water evaporates into the air.

The relative humidity of the air in the bag reaches 100%

The water sublimes into the air.

The bag seals in the moisture.

13.

1 point

"Two objects in thermal equilibrium with a third object are in thermal equilibrium with each other." Which Law of Thermodynamics is this?

Third

Second

Zeroth

First

14.

1 point

On a bitter cold day, the snow is light and powdery. This snow doesn’t begin melting immediately when you bring it into a warm room. Why?

The warmth of the room takes a while to penetrate the snow.

The snow needs to come up to room temperature before it can start melting

The snow needs some time before it can start melting.

The snow's temperature needs to rise to 0 °C before it can start melting.

15.

1 point

Even on a very humid day the hot air from your blow dryer can extract moisture from your hair. Why is heated air able to dry your hair when the air around you can’t?

The moving air carries the moisture off.

Relative humidity drops with rising temperature.

Cold air is wetter than warm air.

Hot air is drier than cold air.

16.

1 point

A plant is a heat engine that operates on sunlight flowing from the hot sun to the cold earth. The plant is a highly ordered system with relatively low entropy. Why doesn’t the plant’s growth violate the second law of thermodynamics?

The plant alone is not the entire system. When you consider the plant plus all its surroundings, then there will be a net entropy increase as the plant grows.

As the plant grows and becomes more ordered, its entropy increases.

The total energy of the system is conserved, so there is no violation.

The plant does violate the second law of thermodynamics, but living things are able to do that.

17.

1 point

"The entropy of an isolated system never decreases." Which Law of Thermodynamics is this?

Third

Zeroth

Second

First

18.

1 point

Why do meats and vegetables cook much more quickly when there are metal skewers sticking through them?

The skewers damage the food and make it more susceptible to being heated.

The metal skewers conduct heat to the interior of the food.

The metal skewers create openings where the heat can get in.

The metal skewers conduct thermal energy to the interior of the food.

19.

1 point

Why does it take longer to cook pasta properly in boiling water in Denver (the “mile-high city”) than it does in New York City?

It's colder at higher altitudes.

Atmospheric pressure is lower in Denver than in New York.

Water has a lower boiling temperature in Denver than in New York.

Boiling is harder at higher altitudes.

20.

1 point

If you add a little hot tea to ice water at 0 °C, the mixture will end up at 0 °C as long as some ice remains. Where does the tea’s extra thermal energy go?

It is absorbed.

It warms up.

It cools off.

It melts some of the ice.

21.

1 point

Why does a pot of water heat up and begin boiling more quickly if you cover it?

No heat is being carried away by evaporating water.

Covered pots boil more quickly.

The lid traps the heat.

The lid makes the pressure go up.

22.

1 point

If you drop a glass vase on the floor, it will become fragments. If you drop those fragments on the floor, however, they will not become a glass vase. Why not?

A fragmented vase has higher entropy than an intact vase.

Actually it could happen, but the probability is very low.

That would violate the first law of thermodynamics.

It isn't possible.

23.

1 point

Which Law of Thermodynamics relates change in internal energy to heat added to a system and work done by it?

First

Zeroth

Third

Second

24.

1 point

Some air fresheners are solid materials that have strong odors. If you leave these air fresheners out, they slowly disappear. What happens to the solid material?

It melts.

It sublimes into the surrounding air.

It dissolves.

It evaporates into the surrounding air.

25.

1 point

It’s often a good idea to wrap food in aluminum foil before baking it near the red-hot heating element of an electric oven. Why does this wrapped food cook more evenly?

The heat reflects off the aluminum, which is shiny.

The foil convects the heat evenly to all parts of the food.

The aluminum foil conducts the heat evenly to all parts of the food.

The foil shields the food from being scorched.