Air in a balloon does 25 J of work while absorbing 81 J of heat. What is the change in internal energy?

Answer 1

Let U be the internal energy. Qin is the heat in and Wout is the work done.

The energy equation for a given constant mass is:

Change in U = Qin - Wout

In your case, that is 81 - 25 = ? Joules

Answer 2

56 J