I think I understand this, but what force lifted the straw in the first place?
skip
-----Original Message-----
From: Forum for Physics Educators [mailto:PHYS-L@list1.ucc.nau.edu]On
Behalf Of Richard L. Bowman
Sent: Thursday, January 19, 2006 2:25 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: fluid
Skip, the force of gravity on the water enclosed by the straw makes the
water level in the straw to move slightly downward as the straw is lifted
thus creating a pressure less than atmospheric pressure inside the straw.
The pressure difference between the outside of straw and the inside
pressure where your finger is keeps the finger "attached" to the straw. If
the force of gravity on the water in the straw becomes greater than the
pressure difference times the area where the finger and straw meet, then
the straw should drop off.
Richard
-------------------------
Richard Bowman
Bridgewater College, VA, USA
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