Heat Transfer Review

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Practice Question

The Concorde supersonic airplane is 20 cm longer when in flight. Explain why.

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Answer

As the jet flies, it experiences a huge amount of friction, which heats it up significantly. This causes thermal expansion, and the plane lengthens.

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Practice Question

What is temperature a measure of?

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Answer

The average kinetic energy of the particles.

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Practice Problem

If you drop a hot rock into a pail of water, the temperature of the rock and the water will change until both are equal. The rock will cool and the water will warm. Is this true if the rock is dropped into the Atlantic Ocean?

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Answer

Yes, yes, yes!!! Even though the Atlantic ocean is huge, the heat that leaves the rock enters the water (law of conservation of energy). This means that the temperature will increase. Since the ocean is a huge body of water, it will be an incredibly small change, but a change nonetheless.

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Practice Problem

When you step out of a swimming pool on a hot, dry day, you feel quite chilly. Why?

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Practice problem

The water will start evaporating in the air. Evaporation requires energy (heat) and that heat will come from your body. Since you are losing heat, you will feel cold.

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Practice Problem

Does a gas give off or absorb energy when it turns into a solid?

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Answer:

It gives off energy, because it is going from high energy to low energy.

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Practice Problem

Why does blowing over hot soup cool the soup?

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Answer

Convection cooling is a very effective method of heat transfer.

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Practice Problem

In a still room, smoke will sometimes rise only so far, never reaching the ceiling. Why?

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