Re: [Phys-l] Definition of upthrust or buoyancy

["Bob Sciamanda" <treborsci@verizon.net>]

You're correct, Chuck.
I have also seen both kinds.
When I wrote "spring loaded" I was thinking of the type which is 
cantilevered to a fixed structure via an elastic arm.



Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsci@verizon.net
http://mysite.verizon.net/res12merh/
-----Original Message----- 
From: chuck britton
Sent: Wednesday, October 20, 2010 11:28 AM
To: Bob Sciamanda ; Forum for Physics Educators
Subject: Re: [Phys-l] Definition of upthrust or buoyancy

I have yet to come across a flap valve that was 'spring loaded' to
return to the closed position.
Gravity does the trick on all the one's I've serviced.
Most have an compartment of air (open on the underside) that helps to
lift it once the seal is broken.


At 11:09 AM -0400 10/20/10, Bob Sciamanda wrote:
> Let me muddy the waters:
>
> Consider the flap at the bottom of a filled toilet tank.
> It snugly covers a hole in the tank bottom.  The hole leads into the toilet
> bowl.
> The flap is held in place by the tank water pressure on its upper surface,
> preventing water flow from the tank into the bowl.  The flap's underside is
> in air.
> When the (pivoted) flap is raised by an added, momentary upward mechanical
> force (via the manual flushing mechanism) the tank  begins to empty into 
> the
> bowl.
> The flap is now surrounded by tank water and floats in an "open position" 
> as
> the tank empties.
> The flap is "spring loaded" so than it can sink to its original "closed
> position" when the tank water level has decreased sufficiently.  Its lower
> surface is again in air and the water pressure on its upper surface holds 
> it
> in place.
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l