When a body is immersed in a liquid,buoyancy is the net force of all the forces acting on it. Now the forces are equivalent to those which will act on the same volume of liquid.Rightly so,but considering the chaotic motion of the molecules of the liquid,for every force acting on that particular volume of liquid,there will be another force in the opposite direction but of different magnitude.The magnitude differs because of the difference in height. Now let's consider a very very thin sheet immersed in the liquid.The opposite forces now will be of the same magnitude as difference in height is negligible and hence will cancel each other!so the only force acting will be its weight. So the thin sheet will never be balanced!So does that imply that no thin sheet will ever float inside a liquid??
Answer
You seem to be considering an (idealised) infinitely thin sheet. You're right that such an object would have no volume and thus displace no fluid --- but it would also have no mass, since its mass is equal to its density times its volume, which is zero. I guess you could conclude that it should have neutral buoyancy, because both its weight and the buoyancy force are zero.
However, one should be careful about this conclusion, because, any real sheet of material will be made of atoms. It will have a finite mass and a finite volume, and its buoyancy will depend on the ratio of the two, as it does for any material.
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