Re: [Phys-l] buoyancy on a submerged pole

[William Robertson <wrobert9@ix.netcom.com>]

Just one correction. If the box is empty, we are removing a downward  
force on the bottom of the aquarium that would be there if the box  
were replaced with water. The downward force on that part of the  
bottom of the aquarium is less than the downward force on the bottom  
all around the box.

Bill


William C. Robertson, Ph.D.


On Nov 3, 2010, at 7:42 PM, Chuck Britton wrote:

> Great - now I'm beginning to understand!!!
> If there is no water under the box we can't call the upward force
> Buoyancy even tho it's still equal to the weight of the displaced
> water.
>
> If we let a monolayer of water seep under the box (but keep it tied
> down with a thread) we can then call the upward force Buoyancy. Same
> amount of force - different name. OK.
>
> Thanx Bill - this clears things up nicely.
>
>
> At 7:24 PM -0600 11/3/10, William Robertson wrote:
> > I agree that the bottom will flex up under the box, but for reasons
> > outlined by others. The pressure exerted on the bottom of the  
> > aquarium
> > just below the box is less than the pressure exerted on the aquarium
> > bottom all around it. Not because of a buoyant force on the box,
> > because you have removed the mechanism for that force, but because
> > there is "less water" above that part of the bottom of the aquarium.
> > And yes, it will be equal to the weight of the water displaced, but
> > that doesn't mean it's a buoyant force pushing up on the box.
> >
> > Bill
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l