eccentrically1 wrote:I can't comment on your example; from what I can tell all you're saying is the weights obey the laws of nature we've been discussing, i.e., KE= 1/2mv2 and P=mv. But it isn't an energy increase. An energy increase would be if the KE of the second weight increased more than 4x, etc.jim_mich wrote:eccentrically1, go back and read the Wiki article with a little more intelligence. It puts some restrictions on the conservation of KE...But when the masses do interact then KE is no longer conserved, while momentum is usually conserved, depending upon the situations.Wiki wrote:It was Gottfried Wilhelm Leibniz during 1676–1689 who first attempted a mathematical formulation of the kind of energy which is connected with motion (kinetic energy). Leibniz noticed that in many mechanical systems (of several masses,
(KE)
was conserved so long as the masses did not interact. He called this quantity the vis viva or living force of the system. The principle represents an accurate statement of the approximate conservation of kinetic energy in situations where there is no friction. Many physicists at that time held that the conservation of momentum, which holds even in systems with friction, as defined by the momentum:
(P)
was the conserved vis viva. It was later shown that both quantities are conserved simultaneously, given the proper conditions such as an elastic collision.
Jimich, go back and read the rest of the article with a little more intelligence. The restrictions are irrelevant to the principle.As an example, if the momentum of a first moving weight transfers to a second equal moving weight such that the second weight gains all the momentum of the first, thus its speed is doubled, then the KE of the second weight is increased 4x, and the sum of the KE of the two weights is doubled. This spontaneous energy increase is compliments of Mother Nature.wiki wrote:
It was largely engineers such as John Smeaton, Peter Ewart, Carl Holtzmann, Gustave-Adolphe Hirn and Marc Seguin who objected that conservation of momentum alone was not adequate for practical calculation and made use of Leibniz's principle. The principle was also championed by some chemists such as William Hyde Wollaston. Academics such as John Playfair were quick to point out that kinetic energy is clearly not conserved. This is obvious to a modern analysis based on the second law of thermodynamics, but in the 18th and 19th centuries the fate of the lost energy was still unknown. Gradually it came to be suspected that the heat inevitably generated by motion under friction was another form of vis viva. In 1783, Antoine Lavoisier and Pierre-Simon Laplace reviewed the two competing theories of vis viva and caloric theory.[3] Count Rumford's 1798 observations of heat generation during the boring of cannons added more weight to the view that mechanical motion could be converted into heat, and (as importantly) that the conversion was quantitative and could be predicted (allowing for a universal conversion constant between kinetic energy and heat). Vis viva then started to be known as energy, after the term was first used in that sense by Thomas Young in 1807.
Jim, did you miss my reply to your post?
The conservation of energy law does include kinetic energy, in cases when masses do interact. When masses (or any components in a system) interact, the friction between them is the reason the law isn't only for thermodynamic systems.
Motion is impossible without friction.
All systems are "thermodynamic" because of their friction: their motion converts some energy to thermal energy, irreversibly.
I think that explains it better.