Buoyancy and apparent weight

[destroyMCAT]

---

Members do not see this ad.

I understand that the bouyancy is equal to the weight of the volume that was displaced, and thus, would be equal to the weight of the object.. but I'm not sure how there is apparent weight if Fb = W.

 

[circulus vitios]

If an object is floating its not accelerating downward (or anywhere else) because...it's floating. F=ma. If acceleration is zero it has no force/weight.

 

[vayntraubinator]

Fb is not = W, the apparent weight.

Fb opposes the Weight, or mg.

So the apparent weight, W = mg - Fb

Imagine you're holding onto a rope suspended in the air, attached to the pulley.

The pulley has a friction to it, so that you won't drop nearly as fast. In fact, just hanging onto the pulley, you and the rope move very slowly downward.

This tension that the pulley has is kinda like the Bouyant force, in that it's pointing in the opposite direction of mg, and thus helps decrease your "apparent weight".

 

[destroyMCAT]

so, what supports the other weight if Fb does not support all of the weight?

 

[vayntraubinator]

so, what supports the other weight if Fb does not support all of the weight?

Obviously, if the object is sinking, Gravity.

ma=mg-Fb

Where a is the new acceleration of the object (the acceleration that goes into calculating the apparent weight)

And if something is floating, then the Bouyant Force is clearly greater than mg.

Fb>mg

So in, ma=mg-Fb, the acceleration would be towards the other direction, pushing the object out of the water constantly.