# Will the box float?

If you submerse an object in water it will float if its density is less than that of water. This is because pressure increases linearly in water as you go deeper, so the bottom of the object experiences more pressure. If you sum up all the forces you will get an upwards force proportional to the volume of the object, regardless of what's in it. Like this box: But what now if we put this box on the bottom of the ocean floor. There will be no water at the bottom anymore to exert pressure. The pressure forces will only point downward so you would expect a large downwards force. There will also be a normal force equal to the weight of the box, so in total you would have zero net force (I think). So is it possible to stick boxes to the bottom of the ocean floor like this? Because my intuition tells me it would still float. • U forgot to add arrows for weight and buoyancy force... Nov 13, 2019 at 11:53
• This is the principle by which suction cups operate.
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Nov 13, 2019 at 17:07

Machinists take advantage of this to make very precise measurements. They make or buy an extremely flat block with extremely parallel faces that are $$1.000000$$ inches apart. And another with faces $$0.500000$$ inches apart. And as many more blocks as they can afford. As little as $$0.000001$$ inch of air between the blocks would spoil their measurements. If the blocks stick together, they know there is less than that much