Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

[Phys-L] Re: Energy & Projectile Lab

I regularly have students measure the effective lengths of air-track-
glider flags in photogates. It should be possible to measure the
effective length of a ball in a photogate. You need to measure the
positions at which the ball first triggers the photogate and last triggers
the photogate. This can be determined by observing the LED on top of the
photogate. Students who rush through this procedure often have large
relative errors in their lab results, but students who carefully measure
the effective lengths have much better accuracy. Using the diameter of
the ball would definitely lead to large errors.

Daniel Crowe
Oklahoma School of Science and Mathematics
Ardmore Regional Center

On Fri, 18 Mar 2005 18:21:45 -0500, Michael Edmiston
<edmiston@BLUFFTON.EDU> wrote:


I have heard of "failures" of the experiment when the teacher uses one
photogate and tries to use the diameter of the ball as delta-x. This is
tough with a round ball because you cannot guarantee the center of the
ball will go through the beam, plus photo gates suffer from a sort of
parallax that makes objects appear thinner than they really are. So
don't use one gate.

Phys-L mailing list