Re: [Phys-l] Finishing up with that Dead Horse.

[Chuck Britton <cvbritton@embarqmail.com>]

At 12:41 PM -0500 11/7/10, LaMontagne, Bob wrote:
> First of all - I have no clue what "flexion" means.

	bending - like a strain gauge.

> However,  The force that the aquarium bottom exerts on whatever is 
> touching it under the "shadow" of the lead cube seems to break down 
> into 3 simple case - and an infinite number of fuzzily defined ones.
>
> 1) The lead cube is suspended by a cable above the aquarium floor by 
> about 1/4 inch. The force against the aquarium flloor - and its 
> force upward against the water is PB (pressure of the water at the 
> level of the bottom of the tank but away from the vicinity of the 
> cube) times the area of the shadow ..... PB*A  
>
> 2) The lead cube (maybe 4 inches across) held up from the floor of 
> the tank by 4 quarter inch diameter dowels. The upward force from 
> the portion of the tank under the shadow is Mg +PT*A-PB*A. Here M is 
> the mass of the cube, PT is the pressure of the water at the top of 
> the cube, and A is the area of the shadow.     (I am obviously 
> neglecting the area of the dowels.)
>
> 3) The lead cube totally osculates the bottom of the tank excluding 
> all water. The upward force from the portion of the tank bottom 
> under the shadow is Mg + PT*A.
>
>
> As far as what occurs for a "rough" surface - I have no clue until 
> "rough" is defined.
>
> Bob at PC


Someone suggested a layer of sand for roughness.
You'd say that sand would be like your dowels in case 2)??