Buoyancy is Imaginary
 

Several months ago, I made this statement during a discussion of
stability here. The minor flame war that resulted made it impractical
to defend the proposition and it wasn't much fun anyway.

While I was away, I had occasion to put together a web site section on
the subject of stability and made the subject line the title of the
first chapter. If anyone is interested in the technical aspects of
what floats their boat with a minimum of math, click:

http://www.rogerlongboats.com/Stability.htm

My son's former physics teacher reviewed the buoyancy section and
pronounced it "Beautifully explained" so it's had some minimum of
vetting aside from being basically a written version of a guest
lecture I used to present to college students.

The last chapter is a brief introduction to the endless foolishness in
the Coast Guard stability regulations for sailboats. This recently
got me an email from a retired inspector saying basically, "Thank
goodness someone finally said something!"

Enjoy

Buoyancy is Imaginary
 

Never argue bouyancy with Roger Long. ;-)

--
KLC Lewis

WISCONSIN
Where It's So Cool Outside, Nobody Stays Indoors Napping
www.KLCLewisStudios.com

"Roger Long" wrote in message
...
Several months ago, I made this statement during a discussion of
stability here. The minor flame war that resulted made it impractical
to defend the proposition and it wasn't much fun anyway.

While I was away, I had occasion to put together a web site section on
the subject of stability and made the subject line the title of the
first chapter. If anyone is interested in the technical aspects of
what floats their boat with a minimum of math, click:

http://www.rogerlongboats.com/Stability.htm

My son's former physics teacher reviewed the buoyancy section and
pronounced it "Beautifully explained" so it's had some minimum of
vetting aside from being basically a written version of a guest
lecture I used to present to college students.

The last chapter is a brief introduction to the endless foolishness in
the Coast Guard stability regulations for sailboats. This recently
got me an email from a retired inspector saying basically, "Thank
goodness someone finally said something!"

Enjoy

Buoyancy is Imaginary
 

Roger Long wrote:
Several months ago, I made this statement during a discussion of
stability here. The minor flame war that resulted made it impractical
to defend the proposition and it wasn't much fun anyway.

While I was away, I had occasion to put together a web site section on
the subject of stability and made the subject line the title of the
first chapter. If anyone is interested in the technical aspects of
what floats their boat with a minimum of math, click:

http://www.rogerlongboats.com/Stability.htm

My son's former physics teacher reviewed the buoyancy section and
pronounced it "Beautifully explained" so it's had some minimum of
vetting aside from being basically a written version of a guest
lecture I used to present to college students.

The last chapter is a brief introduction to the endless foolishness in
the Coast Guard stability regulations for sailboats. This recently
got me an email from a retired inspector saying basically, "Thank
goodness someone finally said something!"

Enjoy



A quote from last week that seems to apply here...

"The need to control has exceeded the need to make sense".


Good work, Roger.


Richard

Buoyancy is Imaginary
 

On Mon, 28 Sep 2009 09:14:57 -0700 (PDT), Roger Long
wrote:

Several months ago, I made this statement during a discussion of
stability here. The minor flame war that resulted made it impractical
to defend the proposition and it wasn't much fun anyway.

Buoyancy may be imaginary but experience has demonstrated that it's
better to be on a boat with it than without.

Buoyancy is Imaginary
 

"Roger Long" wrote in message
...
Several months ago, I made this statement during a discussion of
stability here. The minor flame war that resulted made it impractical
to defend the proposition and it wasn't much fun anyway.

While I was away, I had occasion to put together a web site section on
the subject of stability and made the subject line the title of the
first chapter. If anyone is interested in the technical aspects of
what floats their boat with a minimum of math, click:

http://www.rogerlongboats.com/Stability.htm

My son's former physics teacher reviewed the buoyancy section and
pronounced it "Beautifully explained" so it's had some minimum of
vetting aside from being basically a written version of a guest
lecture I used to present to college students.

The last chapter is a brief introduction to the endless foolishness in
the Coast Guard stability regulations for sailboats. This recently
got me an email from a retired inspector saying basically, "Thank
goodness someone finally said something!"

Enjoy




Way too simplistic, I'm afraid. You seem to attribute buoyancy to gravity
alone. WRONG!

Let's create a system that has 1/100 Earth gravity. Let's place a 1/100
Earth gravity sphere half full of water and half full of air in outer space.
Let's pressurize this sphere to one atmosphere. Let's float a boat in the
water. The boat that weighs a ton only weighs 1/100 ton in this sphere but
the atmospheric pressure is Earth normal. Therefore the pressure upwards on
the boat's hull would be the same as on earth (due to atmospheric pressure)
according to your ill-conceived theory. The boat that is already floating
100 times higher than on earth due to its being 1/100 the weight (mass)
would be pushed even higher. If your theory were correct this would not be
the case.

I rest my case.

Wilbur Hubbard

Buoyancy is Imaginary
 

KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? I think Roger is making a big deal of a very fine distinction.
Its true that an object that is said to be "buoyant" does not generate a
force by itself, the force really comes from water pressure which in
turn is caused by gravity. But, the force is real and buoyancy is
simply a convenient way to aggregate the net pressure on an object. If
there were no force (regardless of what we call it) holding up a ship,
it would sink.

There are, of course, imaginary forces, such as Coriolis which appears
in non-inertial reference frames, but that is a different thing.

Buoyancy is Imaginary
 

On Mon, 28 Sep 2009 17:40:21 -0400, Jeff wrote:

KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? I think Roger is making a big deal of a very fine distinction.
Its true that an object that is said to be "buoyant" does not generate a
force by itself, the force really comes from water pressure which in
turn is caused by gravity. But, the force is real and buoyancy is
simply a convenient way to aggregate the net pressure on an object. If
there were no force (regardless of what we call it) holding up a ship,
it would sink.

There are, of course, imaginary forces, such as Coriolis which appears
in non-inertial reference frames, but that is a different thing.

There are many words in the English language that aren't proper
scientific explanations of a phenomena. Try "beautiful" or "ugly" for
two examples.

Is the fact that there is no scientific justification for the term
"beautiful" reason to stop using it?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Buoyancy is Imaginary
 

On Sep 28, 7:55*pm, Bruce In Bangkok
wrote:
On Mon, 28 Sep 2009 17:40:21 -0400, Jeff wrote:
KLC Lewis wrote:
Never argue bouyancy with Roger Long. ;-)

Why? *I think Roger is making a big deal of a very fine distinction.
Its true that an object that is said to be "buoyant" does not generate a
force by itself, the force really comes from water pressure which in
turn is caused by gravity. *But, the force is real and buoyancy is
simply a convenient way to aggregate the net pressure on an object. *If
there were no force (regardless of what we call it) holding up a ship,
it would sink.

There are, of course, imaginary forces, such as Coriolis which appears
in non-inertial reference frames, but that is a different thing.

There are many words in the English language that aren't proper
scientific explanations of a phenomena. Try "beautiful" or "ugly" for
two examples.

Is the fact that there is no scientific justification for the term
"beautiful" *reason to stop using it?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Roger has the same mistaken impression that many people have, that it
takes energy to hold an object up against gravity. NO, it takes no
energy for a rigid body to hold an object up against gravity. If his
son thinks it takes energy for a table to hold a book up, he needs to
re-learn physics. If you hold a book out with your arm extended, you
ARE using energy because your arm is not a rigid body and you are
exerting energy to keep the muscles tensed. This is equivalent to
holding something up with a leaky pneumatic cylinder. This is
completely different from buoyant forces holding a boat up which takes
NO energy. A buoyant situation that would require energy would be an
object flating within a container at a constant level where the
container has a leak. In that case energy IS required to keep the
object at a constant level because you have to pump in liquid to
replace that that leaks out.
His observation that buoyancy is the result of unbalanced pressure is
trivial in some cases and not entirely accurate in others. A
floating boat has pressure from below balancing the weight from above
and the net buoyant force is simply equal to the weight of water
displaced. A balloon floating in air (or water) has no unbalanced
pressure and the buoyant force is simply equal to the weight of the
medium displaced. A buoyant force is not imaginary simply due to
being a "net force". Forces are vector quantities and the total force
acting on a body is the vector sum of all forces.

Buoyancy is Imaginary
 

There is no such thing as a rigid support.

The book on the table actually does compress the table an amount equal to it's mass.

Buoyancy is Imaginary
 

On Sep 28, 10:00*pm, cavelamb wrote:
There is no such thing as a rigid support.

The book on the table actually does compress the table an amount equal to it's mass.

The book does compress the table slightly but once compressed, no
moire energy is required to hold up the book.

Although I am adamant about buoyancy not requiring energy input, I
think Roger may be nearly right about buoyancy being the result of
unbalanced pressures even for a balloon floating in air. I think it
is related to transfer of momentum of air or water molecules to said
balloon being diff tween top and bottom although after a rum n coke it
aint too obvious to me.
However, consider our balloon as a ping pong ball immersed in a vat of
small lead shot. The lead shot are our water molecules. Shake said
vat to produce thermal motion and said ping pong ball rises to the top
magically.

I never did like the semantics of "imaginary forces" because even for
such so-called "imaginary forces", they can lead to work being done.
Thus the distinction is almost entirely semantics (yeah yeah, I know
frames of reference and all).