AP Physics 2 : Thermodynamics
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Example Questions
Example Question #9 : Work, Enthalpy, And Internal Energy
A gas has a constant pressure of 
The net work is equal to the pressure times the change in volume. So the pressure is 
Example Question #10 : Work, Enthalpy, And Internal Energy
If the volume of a balloon is expanded by 
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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