Re: force and PE without calculus

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 18:33 -0500 10/29/01, Joe Heafner wrote:

> In a calculus-based course, we can illustrate the relationship
> between force and potential energy using the concept of gradient. In
> an algebra/trig-based course, we can't explicitly use calculus so
> what's the best way to demonstrate the force/PE relationship? The
> brute force graphical approach and simply stating that the slope of
> the PE curve is indicative of the force? I was hoping for something
> a bit more elegant.
What's so inelegant about the graphical approach? I think it's pretty
good, myself, and it can be backed up with some nice demos using a
tilted air track. Calculate the grav. force on the glider, and
measure the height and distance the glider passes through in moving
from the beginning to a photogate near the end of the track. Measure
the speed of the glider as it passes through the photogate, and you
can find to a pretty good degree of agreement that F*d = mgh =
(mv^2)/2. Of course F*d is exactly the same thing as mgh, but it's
nice to see that it works out when you measure it.

Put a photogate at the beginning, and you can even show that
velocities don't add in these situations, but energies do-something
that is not always clear to the bheginning students.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

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