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Re: [Phys-l] Errata for FCI?



Regarding this particular question, I don't want to get into trying to read the minds of the original authors. However it is the case that some students think that if there were no air pressure, the object would float off the table. The idea seems to be that things in space are are weightless, so if there were no air, as in space, there would be weight.
So perhaps they were trying to see if students would pick C to determine if they carried this misconception.

joe

Joseph J. Bellina, Jr. Ph.D.
Emeritus Professor of Physics
Co-Director
Northern Indiana Science, Mathematics, and Engineering Collaborative
574-276-8294
inquirybellina@comcast.net




On Nov 3, 2010, at 9:00 AM, carmelo@pacific.net.sg wrote:

M. Horton wrote:
I agree that the original question may not have been asking what it
intended > to ask. So, I'll ask what I think the original
questioner was intending to > ask because I've long had the same
question. (Wow, >that was confusing.) > Where does the buoyant
force come from?

Actually, I am still looking for a more appropriate microscopic
definition on buoyant force. Besides, it seems that many physics
teachers and physics education researchers have misconception on
buoyant force. Perhaps, there should be errata published for numerous
research papers on Force Concept Inventory (FCI)? Please refer to the
question below.

A book is at rest on a table top. Which of the following force(s)
is(are) acting on the book?
1. A downward force due to gravity.
2. The upward force by the table.
3. A net downward force due to air pressure.
4. A net upward force due to air pressure.

A 1 only.
B 1 and 2
C 1, 2, and 3.
D 1, 2, and 4.
E none of these, since the book is at rest there are no forces acting on it.

In many papers on FCI, the answer is D based on the definition that
buoyant force is the magnitude of the weight of fluid displaced by the
body. Perhaps, analysis should be carried out again on FCI based on
the answer C instead? Some of you may prefer B to be the answer? :-)


Best regards,
Alphonsus


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