I am a bit confused about an aspect the "work" part in the first law of thermodynamics, which says that the change in the internal energy of a system is the work done on the system + the heat transferred to the system. Here's my question:
If I do work on, say, a stone, causing it to gain a large total kinetic energy, then according to the first law of thermodynamics (TD), the internal energy has increased. But internal energy simply means the energy contained within the stone, not external energies, such as gravitational potential energy, or, more importantly in this case, the overall kinetic energy of the system. How is the first law of TD consistent with this definition of internal energy? The same problem arises, if, say, I also raise a stone by doing work on it, thus increasing the gravitational potential energy.