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I am suddenly curious: Would a cube placed at the bottom of a tank filled with fluid ($\rho_{\textrm{fluid}}>\rho_{\textrm{object}}$) float?

As far as I know, an object floats if the difference of the force exerted by the fluid at the top/bottom of the object is greater than the gravitational pull. So I think that there would be no buoyancy if there is no pressure to push the object up. Of course it is an ideal situation, but would it be possible for an object to stay at the bottom in this case?

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    $\begingroup$ A heavy object can be attached to a ceiling with a suction cup, so why not a light object attached to the tank floor likewise? $\endgroup$ – Whit3rd Jun 18 '17 at 6:40
  • $\begingroup$ Wow, thinking of it that way, it is way easier to understand! $\endgroup$ – Jihyung Kang Jun 18 '17 at 8:53
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Interesting question. I believe, to arrange such a situation perfectly is near impossible.

Try placing a wooden cube at the bottom of a glass vessel. Hold it down and pour some water into the vessel. Then look at the bottom of the cube from through the glass. You will find that it is wet. The water has somehow made its way through the tiny gaps between the surface of the wood and glass. And in such a situation this water will provide the pressure to boost the cube upwards.

Of course, if you do manage to arrange such a perfect situation then I'm sure the cube will stay at the bottom of the vessel.

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