Date: Wed, 18 Nov 1998 20:14:34 -0800 (PST)
Message-Id: <2.2.16.19981119210900.18770d9e@ed.co.sanmateo.ca.us>
To: "Pinhole Listserv" <pinhole@exploratorium.edu>
From: Art Fortgang <afortga@ed.co.sanmateo.ca.us>
Subject: Re: Pinhole Digest #89 - 11/15/98
I have my physics students build a project as part of their grade. One
group wants to build a Monkey-Hunter apparatus. Anyone know a good design
or a web site where I can direct them?? Thanks for your help
Art Fortgang
At 12:20 AM 11/15/98 -0800, you wrote:
>Pinhole Digest #89 - Sunday, November 15, 1998
>
> Re: Pinhole Digest #88 - 11/14/98
> by "bliss" <swise@lick.pvt.k12.ca.us>
>
>
>----------------------------------------------------------------------
>
>Subject: Re: Pinhole Digest #88 - 11/14/98
>From: swise@lick.pvt.k12.ca.us (bliss)
>Date: Sat, 14 Nov 1998 17:55:40 -0800
>
>My physics students have come up with three questions that we can't come to
>a consensus to among ourselves. Perhaps you all can help -- thanks!
>
>Sarah Wise
>Lick-Wilmerding H.S.
>
>question #1
>
>Can someone explain why friction force is independent of the area of
>contact between the two surfaces? Does anyone know of demonstrations that
>can show this?
>
>It seems that if this is true, it should take an equal amount of force to
>pull a wooden block at constant velocity across a table on its widest face,
>as it does to pull it on its narrowest face. Students who tested this,
>however, found that differing amounts of force were needed to counteract
>sliding friction.
>
>question #2
>
>When an airplane experiences lift, what type of a force is this "lift
>force"? Is it an example of Newton's 3rd law, where air molecules' react
>with an upwards force to the weight of an airplane? This seems too
>simplified an explanation.
>
>Looking at the Bernoulli effect, the greater velocity of air molecules
>above the wing produces an area of low pressure above the wing, so the
>force exerted by the air molecules colliding with the underpart of the wing
>is higher than the force of air molecules colliding on the upper surface of
>the wing.
>
>With all of this in mind, is lift force an example of a larger category of
>forces -- a normal force, for example, or even more broadly electroweak
>forces?
>
>question #3
>
>If a rope is said to break under x amount of weight force, does this really
>mean that it breaks under 2x amount of force?
>
>=46or example, if Harry the 250N mountain climber dangles from a rope which
>will break when >300N of weight is applied (as advertised) and is secured
>to a tree at the top of a cliff, isn't the rope actually experiencing 500N
>of force: 250N from Harry dangling and 250N from the reaction of the tree
>to the pull of the rope?
>
>=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=
>=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=
>=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=A9=
>=A9=A9=A9
>
>Sarah Wise
>
>Lick-Wilmerding H.S.
>755 Ocean Avenue
>San Francisco, CA 94112
>swise@lick.pvt.k12.ca.us
>
>"Not everything that can be counted counts,
>and not everything that counts can be counted."
>--Albert Einstein
>
>
>
>----------------------------------------------------------------------
>End of Pinhole Digest
>
>---------------------------------------------------------------------------
>
>To unsubscribe from pinhole, send an email to requests@exploratorium.edu
>with the words 'unsubscribe pinhole' (without the quotes) in the SUBJECT
>of the email.
>
>To subscribe to the digest and only get 1 combined message a day, send an
>email to requests@exploratorium.edu with the words 'subscribe digest
>pinhole' (without the quotes) in the SUBJECT of the email.
>---------------------------------------------------------------------------
>
>
>
>
Art Fortgang
(650) 726 2820
245 Troon Way
Half Moon Bay 94019
Mills HS