Date: Thu Oct 8 15:03:45 2009

Author: WC Maddox

Subject: Re: Be careful what you ask for (1H10.20)

Post:

From: WC Maddox

According to these Fan Cart instructions from PASCO the cart should move
with the fan blowing against the sail:.
http://hug.phys.huji.ac.il/PHYS_HUG/MAABADA/MABADA_A/Pasco/ci/me-9485/012-05307e/012-05307e.pdf


This may not work on a table due to friction but does work on an air
track. Perhaps the crew of the Mythbuster show could determine if the
PASCO material is correct or whether this is an aerodynamic effect as
suggested below. They could build something that involves firing machine
gun bullets at a metal sail. Put it in a vacuum chamber and put a
slippery liquid on the floor and see what happens.

End Message

cbettis@unlserve.unl.edu wrote:
> Dale,
>
> Right. Actually, if you put the thing on a plate on an air table, it
> will move but that's aerodynamics rearing its ugly head. Vortices form
> at the edge of the sail and you get a low pressure area in the front
> of the sail (note to Dick Berg: I did not mention "you-know-who's"
> principle)
>
> I am also pleased to report that the lecturer wants to intentionall
> puzzle the students and he really didn't expect it to work any better
> than the flat sail.
>
> Cliff


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