AP Physics 2 : Thermodynamics

Study concepts, example questions & explanations for AP Physics 2

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Example Questions

Example Question #9 : Work, Enthalpy, And Internal Energy

A gas has a constant pressure of  as it expands by . What is the net work performed on the gas?

Possible Answers:

Correct answer:

Explanation:

The net work is equal to the pressure times the change in volume. So the pressure is  and the change in volume is . Multiplying the two will equal .

Example Question #4 : Work, Enthalpy, And Internal Energy

If the volume of a balloon is expanded by  against a constant external pressure of , how much heat energy would have to be added in order for the balloon to maintain the same temperature?

Possible Answers:

Correct answer:

Explanation:

We're asked to find the amount of heat energy that must be added to a balloon undergoing expansion against a constant external pressure in order for it to maintain a constant temperature.

The situation being described in the question stem is one of isothermal expansion, meaning that the temperature doesn't change. In other words, we can say that the internal energy of the gas held within the balloon does not change.

Furthermore, we can define the amount of work done by the gas on the balloon as follows.

Combining these expression, we can obtain the following.

Finally, if we plug in the values given to us, we can get our answer.

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