Pushing gravity mechanics

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21 years 9 months ago #4667 by Mac
Replied by Mac on topic Reply from Dan McCoin
mechanic,

Since it is vitrually a mute point but still valid, I'll try to keep it short and hope I do the author justice because he had extensive mathematical proofs and examples that I don't want to post here. If my paraphrased explanation doesn't suffice, I'll try to get a link to those interested so they can follow up.

The cause of the problem is that physics tend to ignore the fact that the object isn't simply free falling. For example the earth moves as well. So when a bowling ball is falling the earth falls toward the ball too.

If you now drop a bowling ball and a feather (in a vacuum of course) at the same time in a test the earth reacts to the collective mass of the feather and bowling ball and that throws them out of sych. I believe it is the heavier object that will reach the earth first.

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21 years 9 months ago #4668 by mechanic
Replied by mechanic on topic Reply from
From Mac

If you now drop a bowling ball and a feather (in a vacuum of course) at the same time in a test the earth reacts to the collective mass of the feather and bowling ball and that throws them out of sych. I believe it is the heavier object that will reach the earth first.


According to Gallileo's principle of addition of velocities the only thing that will be affected is the time it takes for both to reach the ground. The rate of fall will be the same for both. Actually, this was the argument of Galileo. I read that once, Simplicious or something. Draw the accelerations yourself on a piece of paper and see that. Unless I'm missing something.

If G is the constant rate of fall for both and Gb, Gf are the ball and feather rates on earth, then earth has a combined rate of Gb+gf and a velocity V=(Gb+Gf)t. If you consider the earth stationary now, the following are the velocities of the ball and the feather, Vb and Vf:

Vb=Gt+(Gb+Gf)t = (G+Gb+Gf)t =Vf

They hit the ground together but faster than they would hit if they were to be set free each at a time. The difference of course in in the order of 10^-24 sec or something.

In this case I thing people confuse time of fall with rate of fall. But again, I may be missing something.




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21 years 9 months ago #4669 by Mac
Replied by Mac on topic Reply from Dan McCoin
mechanic,

Like I said I'm going to have to go back and find the link to all this because it was complex and he did prove his point(s).

It wouldn't affect rates but just starting objects from the same height has a problem. If the center of mass is set equal then one reaches earth before the other. And likewise if you set them on a common shelf, the center of mass is unequal and their velocities cause one to over take another. But I'll get back to you on this.

I'm going to be out of town this weekend. Going to Phoenix to see my oldest son and see my ROPE baby run. (See my home page).

Mac

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21 years 9 months ago #4864 by Larry Burford
Here is another way to try to figure this out:

Take three absolutely identical objects to the top of your drop tower and let them go. All three objects will fall with exactly the same acceleration, reach exactly the same speed and take exactly the same time to reach the ground.

No ifs, ands or buts. Right?

=============

Now, attach two of these identical objects together with a massless bolt. (Yes, you really can do this. In the real world.) Take the three (uh, two) objects up the tower and drop them again. Both objects will fall with exactly the same acceleration, reach exactly the same velocity and take exactly the same time to reach the ground.

But now one of them has twice the mass of the other, and they no longer have the same shape.

Any ifs, ands or buts?

Regards,
LB

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21 years 9 months ago #4865 by Jim
Replied by Jim on topic Reply from
The equal and opposite fall of the Earth is missing in the posts above The Earth is accelerated into the greater mass at a higher rate and so it should reach the greater mass first-right?

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21 years 9 months ago #4866 by MarkVitrone
Replied by MarkVitrone on topic Reply from Mark Vitrone
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I have the following question for the pushing gravity experts:

Assume vacuum space. Two small metal cylinders, one 10" long with an 1" radious (slim) and the other 1" long with a 3.1622776" radious (fat), so both having the same volume and mass for that purpose. The cylinders have a different surface area.

According to free fall physics, if dropped from 100 meters both will reach the ground at the same time, acceleration of gravity being independent of mass.

I now align both along their height and let them drop. Obviously, the area of the fat cylinder getting gravitons from the top is much larger than the area of the slim cylinder. How can it be true both cylinders dropping at the same rate all along the way?


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Another point about matter that needs to be mentioned is that even for a dense metal like Hg or Pb, there is still ~99.9% empty space in each and every atom of the solid and as you increase energetic phases, this number more closely approaches 100%. Studies of matter near 0 K always show a small amount of heat absorption even under extreme experimental care. I think this heat is due to graviton absorption. I am curious about how this mechanism may relate to particle decay and construction. Any ideas? MV

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