- #1

pkh

Thank you !

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- Thread starter pkh
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- #1

pkh

Thank you !

- #2

HallsofIvy

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If forces are not "balanced" around the center of mass, the will be a rotation that a force applied to the center of gravity would not cause.

- #3

pkh

Originally posted by HallsofIvy

If forces are not "balanced" around the center of mass, the will be a rotation that a force applied to the center of gravity would not cause.

Well, Acsimet force is the force applying on an object in a liquid (such as water, oil, etc). The intensity : F=V.Gamma

where

V-volume of the part in water of object

Gamma-specific weight of the liquid

In the case where the object in the lique is liberal (not linked to anything who is n't in the lique), I'm agree too with you about the reason why the force acsimet applying at the centre of gavity, if not the rotation is obvious.

But there 're the others cases, you can click on this link for an example:

http://www.ttvnol.com/uploaded/PKH/Acsimet%20force.gif

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- #4

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pkh,

I think by 'Acsimet' you mean 'Archimedes', and what you're looking for is the point of application of the buoyant force, which is the center of volume of the submerged part, see here:

http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module4/basics.htm [Broken]

I think by 'Acsimet' you mean 'Archimedes', and what you're looking for is the point of application of the buoyant force, which is the center of volume of the submerged part, see here:

http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module4/basics.htm [Broken]

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- #5

pkh

Originally posted by arcnets

pkh,

I think by 'Acsimet' you mean 'Archimedes', and what you're looking for is the point of application of the buoyant force, which is the center of volume of the submerged part, see here:

http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module4/basics.htm [Broken]

Well, I made a mistake with "Archimedes" . Thank you for the link .

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- #6

pkh

Originally posted by arcnets

I think by 'Acsimet' you mean 'Archimedes', and what you're looking for is the point of application of the buoyant force, which is the center of volume of the submerged part, see here:

http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module4/basics.htm [Broken]

I read all but the object in the explaination is libre (it has no link with the other object which aren't in the water). Moreover, I don't understand the symbol of triangular shape. What does it mean, that mathematical symbol ?

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- #7

HallsofIvy

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PKS: There are links at the site: the "dots" on the left (although unlabeled) are links to other "pages" of the document. I didn't see any triangular mathematical symbol. At the end, there is a triangle inside a disk which is clearly a "next page" link.

- #8

pkh

Originally posted by HallsofIvy

PKS: There are links at the site: the "dots" on the left (although unlabeled) are links to other "pages" of the document. I didn't see any triangular mathematical symbol. At the end, there is a triangle inside a disk which is clearly a "next page" link.

Rehi ;-),

Yes, you're right, I'm not english but I'm not french too (although I can use both of those 2 languages) :-).

And the symbol which I don't understand, you can see here

.http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/module4/equilibrium_stability_files/image002.jpg [Broken]

I always wait your explains.

P.S: My nickname is PKH, not PKS .

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- #9

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That stands for the gradient. The partial derivative of the components of the vector p.

- #10

HallsofIvy

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meister is correct that the upside down triangle is the "gradient" (sometimes read "del"). His explanation is a little opaque. The gradient of a function of several variables is the vector whose x component is the derivative with respect to x, y component is the derivative with respect to y, etc.

The gradient vector has the nice that it always points in the direction in which the function increases fastest and that it's length IS that fastest increase. Of course, at a point of maximum value the function will not increase so it has no direction of fastest increase (and since fastest decrease is opposite to the direction of fastest increase, at a minimum there is no direction of fastest increase) so the gradient must be 0. This is exactly the same as the more basic idea that at a critical point, the derivative is 0. In fact it is more correct to think of the gradient as THE derivative of a function of several variables than the partial derivatives.

Since most physical laws can be expressed as minimizing or maximizing something, they typically involve the gradient.

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