Can you shape a buoyant object stuck to the bottom of a body of water such that it floats?

Question

I understand that an object, say a closed plastic cube full of air, stuck to the bottom of an aquarium with a smooth glass bottom will not float if you firmly place it such that no water can get underneath. What if you change the shape such that you add surfaces that water CAN get under to provide lift? Take the cube and change it into a T shape for instance. Now the horizontal part at the top DOES have area under which water can provide lift. Will this break the suction holding the bottom of the T to the bottom of the aquarium and cause it to float?

NMech · Answer

In the majority of the scenarios (material type, thickness of walls, width of T flannges etc) the difference on pressure in the flanges will be greater that the adhesive force keeping it to the bottom.

Answered by NMech on April 22, 2021

kamran · Answer

let's annotate the following

m = weight of the object
H = height of the object's flange
D is the depth of the water to the top of the object
rho.g.D is the pressure of water on the top
rho.g.(D+H)= the pressure on the bottom of the flange
L= width of the object
we assume the thickness of the object as 1 for now.

The trapezoid areas of the pressure on the sides cancel out.
when $ rho.g.(D+H)2B geq m+rho .g.D.L$ the buoyancy will float the object.
.

r13 · Answer

The object will flat if sum of the upward forces is more than the sum of downward forces. When the sum of the upward forces equal to the sum of the download forces, the object is in the "limiting equilibrium" condition, instability and floating will follow.

Can you shape a buoyant object stuck to the bottom of a body of water such that it floats?

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