From: Ron DeFronzo (rdefronz@ride.ri.net)
Date: Mon Jul 19 1999 - 06:15:10 PDT
Date: Mon, 19 Jul 1999 09:15:10 -0400 (EDT) Message-Id: <v01530501b3b898e858cf@[131.109.12.76]> From: rdefronz@ride.ri.net (Ron DeFronzo) Subject: Re: IFI-list Balance Inquiry draft complete
Hi Fred,
A couple of thoughts on the balance inquiry workshop. I sat in on the
session at NSTA Boston and thought it was wonderful. I'm going to offer it
in late August to our teachers including middle/high school teachers. This
particular session is a great opportunity to get a high school physics
teacher involved as a content specialist in our work with elementary
teachers.
I'm going to add a few of my own ideas to the workshop so as to make direct
connections with the kits we use. Specifically, in the STC Magnets and
Motors kit there are at least two good connections. The first comes when
students are asked to create their own compass using two magnets on the end
of a straw and balance it on a cup using a common pin. I've found that
teachers have a difficult time balancing this because they don't understand
the idea of center of gravity and build their device with the weights too
high. Keeping the weights low helps, and this is directly addressed in
your inquiry workshop. Also moving the weights closer or further from the
fulcrum is addressed.
The second connection comes from the same kit in building the spinning
motor using a coil of wire. In order for this to spin smoothly, it's
important that the coil be constructed so that it spins about its own c of
g; otherwise it never really gets going. I'm going to bring in my own
variable speed drill and attach large pieces of irregularly shaped
cardboard where the point of rotation is off from the c of g. Then have
the teachers locate the c of g using plumb lines and spin the cardboad at
high speed on the end of the drill. I think this will help to bring home
the reason why anyone would be concerned about a point called the c of g
where all the mass "seems" to be.
One more connection we will make is with the FOSS Balance and Motion kit
when the students construct the spinners using buttons and string. These
devices also need to spin about their c of g.
I'd be interested in any more connections to kits around this topic that
others might come up with.
I love this workshop because it combines the best elements of an inquiry
session with substantial content development directly tied to the kits. I
highly recommend finding more ways to make this connection.
Ron
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Ron DeFronzo
East Bay Educational Collaborative
P.O. Box 754
Portsmouth, RI 02871
401-683-5151 x305
fax 401-683-6805
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