Question

How is the weight of an object, the weight of water and the boyancy forces related?

I know that
Weight= Boyancy forces so:
Dobj*Volobj*gravity=Denswater*gravity*volumewater

Answer 1

but how is the weight of the water related there?

Answer 2

The weight of the water IS the RHS of the equation.

\[\rho_{water}*g*V_{water}=W_{water}\]

Answer 3

Yes, buoyancy equals the weight of the water displaced.

Answer 4

Yes...I did buoyancy=weight of the object. But how is the weight of the water related? So the three are equal?

Answer 5

The upward force of the water turns out to be equal to the weight of the water displaced by the volume of the object that is submerged.

Imagine a waterproof pancake of thickness d and area A that is submerged and horizontal. The pressure of the water downward on the top of the pancake is rho.w g h and that upward on the bottom is rho.w g (h + d), where rho.w is the density of water. Force is pressure times area, and the difference between the downward pressure force and the upward pressure force is just F = (net pressure)(area) = rho.w g A d, but A d is the volume of the pancake, so F = density of water times volume displaced times gravity = weight of water.

Answer 6

Ok...got it perfect until there...I got that the buoyancy is the same than the weight. But how is the weight related to this?

Answer 7

The upward buoyancy force is equal to the weight of water displaced by the submerged volume of the object. If the object is wholly submerged, that volume is the volume of the object. If the object is only partly submerged, then that volume is however much volume is submerged. If only partly submerged, the weight of water displaced will also be the weight of the object. The object sinks to the level at which the weight of water matches its weight. If it is too heavy, it keeps sinking and then its apparent weight underwater is its original weight minus weight of water displaced.