Intro to Buoyancy and Archimedes' Principle [Physics of Fluid Mechanics #28]

[@_Felineself]

Thanks a lot for the easy explanation

[@alexandarbezanovski5192]

I've watched so many buoyancy videos and did not get it, you my friend, explained it perfectly!

[@SimmySigma]

I’m so glad to hear the video helped! Buoyancy can be hard to understand but I’m glad you got through it. :)

[@mochcha]

Very nice and clear explanation

[@ashleenrai570]

Great video!

[@ahmedmokkedem7525]

Thanks so much.

[@vibhasheenansree1337]

OMG Thanks a bunch

[@captainamericawhyso5917]

The thing is that objects don't just stay submerged inside a volume of water. They either float or sink. This proof of buoyancy doesn't really prove anything, it doesn't describe at all a real life objet in the water. I also saw your video of a floating object hoping to find a better explanation there, but nothing. You just used the buoyancy formula that you prooved for a submerged object to the floating one without explaning how. When an object floats there isnt any water above it(no force down) so how whould we proove the buoyancy force there?

[@SimmySigma]

You’re correct! Those objects do not remain submerged because of the buoyant force acting on them. But the buoyant force itself is simply the net force acting on the object due to the amount of liquid that is displaced. That same buoyant force is what causes objects to move upwards if you submerge them. And when an object is floating at the top of some body of water, it’s still displacing a tiny bit of fluid, given that part of the object is below the water line. That displaced liquid is what causes the buoyant force to act on that object. It’s true that there isn’t water above the object when it’s floating, so the pressure at the top due to the liquid is 0. However, there is still water below the object at some depth and, therefore, pressure. That pressure acting on the bottom surface would result in an upward force. The force at the top would be 0. But the net force on that floating object is still the buoyant force. I hope that made sense and sorry for the long explanation! Just wanted to make sure I could answer the question clearly. :)

[@captainamericawhyso5917]

​@@SimmySigma Thank you for taking the time to reply🙏. I understand that it is the buoyant force that causes objects to move upwards or downwards, the thing i disagree with is this formula derivation. Drawing an object that seems to just stay submerged, like its in equilibrium and then figuring out the forces acting on it, seems wrong. Shouldn't we derive the formula when the object is floating like you did in your video: kzbin.info/www/bejne/aKbKaHx3r7Cpr9E Physics of Fluid Mechanics #36

[@SimmySigma]

@@captainamericawhyso5917 no problem! Ah I can see why drawing the object as if it were stationary might have been a source of confusion. I suppose I should have clarified and mentioned that the buoyant force we calculate in this video is meant to be instantaneous. So imagine taking a basketball and submerging it below the waters surface. You’ll notice that it’s pretty tough to do because the buoyant force is strong. Now, imagine letting the ball go while it’s fully submerged in the water. The ball will shoot straight up! Now, when you have the ball submerged with your hands, there is still buoyant force acting upwards on the ball. And the instant you take your hands off, there is still buoyant force acting on the ball. So for the sake of this derivation, the scenario that we’re focused on is the exact instant you remove your hands from the ball. At that point in time, the ball is submerged and the only forces acting on the ball are it’s own weight and the forces derived from the pressures below and above the ball which yield the buoyant force. I hope that makes sense and clarifies any confusion! :)

[@glykerkele6651]

@@SimmySigma yes exactly, thank you very much once again🙏😁