I guess all those big ships with water ballast tanks are just
pretending.

Scotty


"DSK" wrote in message
. ..
Dave Doe wrote:
a) What is the *point* of your experiement? - other than to
only prove
my argument correct.


Dave, since your argument is not correct, it would be pretty
hard to prove.

Are you saying that the water ballast inside a boat hull
does not affect it's stability? That the water ballast
"weighs nothing" until it is above the waterline?

If that were true, the boat's waterline would be the same
when the ballast tank was empty as when it is full.

Does the boat's displacement increase when the ballast tank
is filled? If so, then the the water ballast "weighs"
something, regardless of where it is relative to the waterline.

If the unit conter of gravity is below what the boat's
Center of Gravity would be without the ballast, then it
increases the boat's stability, regardless of whether the
tank is above or below the waterline.

b) try this (your experiment pretty much, say 4) ...

So 3/4 full. Hold the bottle at the top and note the weight.
Slowly
lower it into the water. Note the weight changing! ??? How
can it be
getting lighter all by itself?


Try this experiment.

Float an empty bottle. Mark where the waterline is.

Now fill it however full you want, 1/4 or 3/4 or whatever.

Does the bottle sink any deeper into the water?

No?

Then it "weighs" more, the water inside the bottle must be
weighing it down.



PS: experiment not conducted, just using simple physics.
Feel free to
do it and get back to me if I'm wrong.


Yep, it's just simple physics. But a number of people have
tried to proclaim that water ballast can't possibly work
because "water doesn't weigh anything in water." But it
obviously *does* work, and the physics (when considered
correctly) show why.

Fresh Breezes- Doug King