Re: motion sensors

["Spagna Jr., George" <gspagna@RMC.EDU>]

Carl Mungan writes:

> a simple experiment I do early on is have the students
> drop a tennis ball onto a motion sensor to determine g and students
> often have trouble getting good data. But smoother balls are usually
> harder - do folks protect their sensors from impacts? We often use a
> grille on a frame boxing the sensor but I suspect these introduce
> some noise. (Or students can catch the ball at the last minute but
> they are often not coordinated to do this without disturbing the beam
> earlier.)

We point the motion sensor at the floor and drop the balls from a point
under the sensor, which means we can drop everything from ping pong balls to
basketballs without worrying about damage to the sensor.  Repeated bounces
can be used to obtain a coefficient of restitution.  We've not had
significant problems with detecting tennis balls - our biggest problem is
that they tend to bounce out of the beam.

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George Spagna
Department of Physics
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505
phone: (804) 752-7344
FAX (804) 752-4724
e-mail: gspagna@rmc.edu
http://www.rmc.edu/~gspagna/