Is there proof gravity can not be a energy source?

[ResinRat2]

Ok, I should have said that the weight was lifted infinitely slowly so as not to instill a velocity (Kinetic Energy) to the weight.

RR2

[Omnibus]

Ok, I should have said that the weight was lifted infinitely slowly so as not to instill a velocity (Kinetic Energy) to the weight.

RR2

That's fine but in reality the velocity of lifting is finite. So, CoE goes, right?

[ResinRat2]

I don't understand the point of that. The velocity of lifting does not come from gravity, it is instilled into the weight by the force that is used to lift it. Once the weight is in motion downward then gravity gives it momentum, yet this momentum is lost on the way upward again. So there is no net gain in energy.

In order to complete the circle again, more energy must be supplied to push the weight upward again.

Again, no net gain. Only loss. This is how I understand it works.

Sorry, Omnibus, what do you think I am missing here?

[brian334]

Mr. Rat,
Your example is to limited to prove gravity can not be used as a energy source.
But at least your on the right page.

[Omnibus]

I don't understand the point of that. The velocity of lifting does not come from gravity, it is instilled into the weight by the force that is used lift it. Once the weight is in motion downward then gravity gives it momentum, yet this momentum is lost on the way upward again. So there is no net gain in energy.

In order to complete the circle again, more energy must be supplied to push the weight upward again.

Again, no net gain. Only loss. This is how I understand it works.

Sorry, Omnibus, what do you think I am missing here?

The point is the following: thermodynamics only considers the energy of the ball itself, that is, how much energy a ball has at a given moment. When lifting the ball at the moment it reaches height h it not only has energy of position mgh but also has kinetic energy (1/2)mv^2. The ball has it, right? Thus, the ball at height h in this case has energy mgh + (1/2)mv^2. If we decide to keep it at height h, have it there at rest, the ball now will only have energy mgh and if we then let it go back to the floor only that energy mgh will be recovered. The kinetic energy (1/2)mv^2 will not be recovered. There is nothing that can comensate for the kinetic energy (1/2)mv^2 which was lost by the ball. That's a violation of CoE in purely classical terms, inherent in theoretical mechanics. Is that clearer?