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

[John Mallinckrodt <ajm@csupomona.edu>]

The glue is irrelevant except for its role in preventing seepage.  I thought we'd already dealt with this via Curtis' illuminating suggestion to get rid of the glue and cut a (well-fitting) hole in the floor of the aquarium.

If you prevent seepage there is simply nothing OTHER than the bottom of the aquarium that is even ABLE to exert an upward force on the box.  Since there ARE other downward forces (i.e., "gravity" and the downward force from the water) and since the box IS just sitting there, the bottom HAS to exert an upward force on the box.  

Draw a free body diagram.

John Mallinckrodt
Cal Poly Pomona

On Nov 3, 2010, at 6:06 PM, Chuck Britton wrote:

> At 5:48 PM -0700 11/3/10, John Mallinckrodt wrote:
> > I don't understand this.  There is no upward force being exerted on 
> > the bottom of the aquarium by the box.  How could there be?  What 
> > mechanism do you envision by which the box could possibly exert such 
> > a force?
>
> The glue.
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