Chronology Current Month Current Thread Current Date [Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

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

I should also point out that you cannot simply assume that this supporting force N is the same in value for the two situations (water blob vs object).

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsci@verizon.net
http://mysite.verizon.net/res12merh/

--------------------------------------------------
From: "Bob Sciamanda" <treborsci@verizon.net>
Sent: Thursday, October 21, 2010 8:12 AM
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Definition of upthrust or buoyancy

. . . - the blob could be on the bottom of a glass beaker.

Except that the upward rigidity force N of the beaker bottom on the
blob/object now enters the calculation.

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsci@verizon.net
http://mysite.verizon.net/res12merh/

--------------------------------------------------
From: "LaMontagne, Bob" <RLAMONT@providence.edu>
Sent: Wednesday, October 20, 2010 12:02 PM
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Definition of upthrust or buoyancy

If you want to imagine the buoyancy on an object, first imagine a blob of
water with exactly the same shape as the object. That water is obviously
in equilibrium. Integrate the pressure over the surface area of the blob.
If in equilibrium, this must give a force that is equal and opposite to
the weight of the water. Now replace the blob with the object. The
surfaces forces have not changed so they still add to the weight of the
blob. Hence, the buoyant force is the weight of the water displaced. This
definition of buoyancy does not require water surrounding all surfaces of
the blob - the blob could be on the bottom of a glass beaker.

As John D. has pointed out, stickyness is a different issue.

Bob at PC

_______________________________________
No infections found in this outgoing message
Scanned by iolo System Shield®
http://www.iolo.com

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

_______________________________________
No infections found in this incoming message
Scanned by iolo System Shield®
http://www.iolo.com

_______________________________________
No infections found in this outgoing message
Scanned by iolo System Shield®
http://www.iolo.com