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Greetings,
Ok, I am stumped by the Physlet on fluids found at (among other place=
s):
http://webphysics.davidson.edu/physletprob/ch8_problems/ch8_11_fluids=
/fluids_2.html=20
The alleged answer is that "B" is the only "physical" animation, but =
I do not see why the block of wood will float higher in this animatio=
n as oil is drawn away but before the block of wood breaks the surfac=
e of the oil.
By Archimedes Principle and the equilibrium principle, the weight of =
the block (constant) should equal the weight of the fluids displaced;=
which would be the sum of the (oil displaced)'s weight and the (wate=
r displaced)'s weight. Why would the ratio of these two weights chan=
ge when the block is less deep under the oil?
If we calculate the buoyancy force based on the difference between th=
e water's pressure pushing up on the bottom surface of the block and =
the oil's pressure pushing down on the top surface, again I do not se=
e why this "difference" would be different before the oil no longer c=
overs the top surface of the block.
Animation "A" does not seem physical to me because once the block is =
no longer under the oil, it should sink deeper into the water.
I would appreciate someone else's insight into this.
Thanks,
Stuart Leinoff
Professor of Physics
Science Division Chair
ACC