Kinetic Energy

[FishBox]

Here's something that's bothered me for years: If you took a snapshot in time of a ball rolling along a table, how would it differ from a similar, but stationary, ball? How could you tell (by looking at it's atomic structure, or whatever method you like) that it was moving? How does kinetic energy manifest itself in a moving object? Thanks.

[sddsddean]

I've had a quick think about this and I dont think you would be able to tell. As one of the variables in Kinetic Energy is velocity, which is time based (velocity=distance/time), you must have a time based perspective (eg two different photos) to 'appreciate' it as a rolling ball. I can't see that the atomic structure would be appreciably altered, unless it was a really squishy ball, so that the surface in contact with the table deformed. As it rolled along different atomic bonds would get deformed as it rolled along, but unless they were all labelled seperately, you wouldn't be able to tell one bond from the other (as in looking at 2 photos).

[FishBox]

Re-reading my post, I don't think I've phrased my question right. I'll try again. Ummmm, how does the BALL know it's moving at any given moment? Where is the force that's moving it along actually located? Movement is a product of time, but at any point IN time there must be some quality of the moving object (or the space around it, or whatever) which 'tells' it that it's moving, otherwise it wouldn't be. Jeez, this reminds me of stoned conversations I used to have with mates. :)

[Gef]

I think that you are both stoned. We know it's moving because it doesn't stay in the same place. It doesn't know it's moving because balls can't think and atomic structure has nothing to do with it :-)

[sddsddean]

The ball doesn't know its moving as it is an inanimate object and therefore has no brain. The force that moves it is an outside force eg gravity or 'you pushed it'. Its movement is a result of Newtons 3rd law "Every action has an equal and opposite reaction". There is nothing that 'tells' it its moving; it just follows the dynamic laws of Newtonian physics. (Off for a quick spliff!!!)

[smithy]

if it's on a slope, a whole bunch (physics term) of mass on the lower side is outside it's CofG which creates a torquey turning force, whose name I'll remember in a moment