A question about gravity

[jammieg]

I don't understand this, the potential energy explanation of gravity says that if i drop a rock it's energy is converted into kinetic energy of motion as it falls, so that the higher up it is released the more energy it has kinetically when it hits the ground, both balance out the potential and kinetic energy so that no energy is created or destroyed just converted from one form to another, makes sense...

but my question is when the rock hits the ground and stops, gravity still affects it right at the atomic level? Does that mean it's still falling on the atomic scale? Creating pressure thereby heat?

[swansont]

The atomic forces are quite strong and that motion is very quickly dissipated into the vibrations that show up as an increase in temperature, and sound.

[alpha2cen]

I don't understand this, the potential energy explanation of gravity says that if i drop a rock it's energy is converted into kinetic energy of motion as it falls, so that the higher up it is released the more energy it has kinetically when it hits the ground, both balance out the potential and kinetic energy so that no energy is created or destroyed just converted from one form to another, makes sense...

but my question is when the rock hits the ground and stops, gravity still affects it right at the atomic level? Does that mean it's still falling on the atomic scale? Creating pressure thereby heat?

 

That's the calculation skill problem.

The problem is how large you set the system size.

If you set the system as the space from the starting point to the end point, you can only get the kinetic energy as a result of the potential energy change.

But if you make the system more larger - the Earth, your can get kinetic energy plus remaining potential energy as the calculated result.

[lemur]

I've been criticized for saying this, but I think it makes sense: a rotating planet can be described as having a certain centrifuge effect, which can be considered to reduce its net gravity. Think of what would happen if the Earth accelerated in its rotation. At some point, objects would start to be pulled from the ground and flung into outer space. Prior to that, they would be losing weight due to decreasing gravity. So, from another point of view, any object that appears to be standing still on the ground is actually "falling" together with the rest of the ground, whose "fall" is impeded by all the other ground underneath it. The rotation of the planet is the net rate of the whole "traffic jam" trying to fall together. Again, if it were falling totally unimpeded, it would be a swirling dust-cloud instead of a ball of condensed solid matter. So the kinetic energy of, say, a tree is the motion it expresses by rotating along with the rest of the matter that makes up the planet. Its potential energy is how much it would accelerate if it could continue to fall through the ground unimpeded (if, for example, the ground was suddenly a swirling dust-cloud).