Re: Newton's 2nd law lab

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

To amplify on my last reply to David.  The modified Atwood's machine is used
as a quasi one-dimensional problem.  The frictionless pulley changes the
direction of  the force (the tension in the string) from the vertical to the
horizontal direction, but the dynamics/kinematics of the cart are considered
as a one dimensional problem.  As such, IT is a convenient way to apply
easily determined forces that can cause horizontal motion.  It IS NOT a
complicated problem when viewed in these terms.

Rick

{When this kind of lab is done with my science majors, they have worked with
the modified Atwood's machine problem prior to the lab and thus are familiar
with this idea of transferring the vertical force to the horizontal
direction.  For my non-science majors, they never question the assumption
that the falling mass provides the force that is pulling horizontally on the
cart. ;-)  }



-----Original Message-----
From: Herb Schulz <herbs@INTERACCESS.COM>

> Howdy,
>
> The problem is that we understand Newton's Second Law and believe it and
> the combined mass of two objects moving in two different directions comes
> by combining the 2nd Law equations for each object.  This is not at all
> obvious to many others (including that parent!) and certainly not to those
> folks we are trying to get to understand Newton's 2nd Law.
>
> Good Luck,
>
> Herb Schulz
> (herbs@interaccess.com)