Message-Id: <3.0.3.32.19971203122334.0069c554@mail.walltech.com>
Date: Wed, 03 Dec 1997 12:23:34 -0600
To: pinhole@exploratorium.edu
From: geoff ruth <geoffr@eastside.org>
Subject: Re: vector components
In-Reply-To: <l03102804b0ab4815a635@[153.90.236.25]>
Wait! I'm confused too -- I'm with your kids. I think that gravity does
pull only straight down. I think that the reason that the ball (or whatever
it is on the ramp) is moving at an angle is because the ramp is exerting a
normal force perpendicular to the surface of the ramp. When you do vector
addition to combine these two forces, then you get something that points in
the direction the ball actually moves. Only if you take a coordinate system
where y (or x) is not parallel to the direction of the force of gravity,
will you split up the force of gravity into components.
Maybe that's what you actually did in class, is set up a coordinate system
where x is parallel to the table's surface. If so, then I think that the
conceptual difficulty might be one that has to do with the idea of
reference systems and relative coordinates.
Let me know where __my__ confusion lies.
-Geoff Ruth