Bouyancy and Normal force at a fully submerged object

Asked Oct 16 '21 at 13:28

Active Oct 16 '21 at 14:57

Viewed 18 times

I learned as a child that

in a fully submerged object (which is touching the bottom of the fluid tank), the normal force "N" by the tank's bottom to the object is N=weight-bouyancy.

However I recently understood that bouyancy is just a simple way to use pressure difference by gravity. If so, considering a cylinder in a fluid with a top surface A, There are mainly three vertical forces. 1. Force P*A due to pressure on top surface 2. W due to gravity 3. Normal force N by tank bottom. Then, isn't the normal force N=W-PA?.

I think The main difference is whether there is fluid to give pressure at the bottom surface.

Do I understand bouyancy or normal force wrong? Isn't pressure just another form of normal force? I really appreciate your help.

edited Oct 16 '21 at 14:57

Qmechanic

201,751

asked Oct 16 '21 at 13:28

Med

https://physics.stackexchange.com/a/516148/231654 Possible Duplicacy. The first post should answer your question. BTW, the latter expression should be $N= W + PA$ and not $N = W - PA$ – Anu3082 Oct 16 '21 at 14:06
wow you're right. Thanks!!! – Med Oct 16 '21 at 15:01
btw should I delete this question?? – Med Oct 16 '21 at 15:02
@Med Just leave the question and we will mark it as a duplcate. – John Rennie Oct 16 '21 at 15:20
2

Does this answer your question? Does buoyant force vanish if there is no liquid below an object? – Jon Custer Oct 16 '21 at 17:53

Bouyancy and Normal force at a fully submerged object

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