- #1
etotheipi
Goldstein, the oracle of classical mechanics, says:
But Morin also reliably tells me that
These two definitions contradict in their treatment of external conservative forces. Morin only counts the action of internal conservative forces in the definition of the potential energy of the system, whilst Goldstein also includes those of external conservative forces. Both are mathematically sound, but I think Morin's definition is better. This is because the work done by a single external conservative force in a pair cannot always be written as the negative of a change in a potential energy function on its own (e.g. if the position of the external body exerting the force is changing).
I wonder then what forces contribute to ##\sum V_i##. The only examples I can think of that would be perfectly fine to include in that term are the potential energies of fictitious/inertial forces, for which there are no other source bodies that we would otherwise need to include in our system. I wondered whether anyone could clarify what other forces contribute to that first term? Thank you.
But Morin also reliably tells me that
[The total energy of the system] may come in the form of (1) overall kinetic energy, (2) internal potential energy, or (3) internal kinetic energy
These two definitions contradict in their treatment of external conservative forces. Morin only counts the action of internal conservative forces in the definition of the potential energy of the system, whilst Goldstein also includes those of external conservative forces. Both are mathematically sound, but I think Morin's definition is better. This is because the work done by a single external conservative force in a pair cannot always be written as the negative of a change in a potential energy function on its own (e.g. if the position of the external body exerting the force is changing).
I wonder then what forces contribute to ##\sum V_i##. The only examples I can think of that would be perfectly fine to include in that term are the potential energies of fictitious/inertial forces, for which there are no other source bodies that we would otherwise need to include in our system. I wondered whether anyone could clarify what other forces contribute to that first term? Thank you.