🚀 go-pugleaf

I am trying an impulse - change in momentum experiment with my students
and we are getting a 30% error.  Let me explain.
1.  By sending a glider across an air track, a rubber bumper on the glider
collides and rebounds off a force probe.  Measuring the area under the
F*delta t graph (using MacMotion software) we can compare the impulse with
the change in momentum of the glider.  This works within a few %.  No
problems.

2.  Now we set up a Bungee Jumper using a Troll that is pushed off a
platform with a long rubber band attached to the Troll's ankle and a force
probe.  The velocity of the falling Troll is calculated just before the
rubber band begins to stretch.  Knowing the change in momentum of the
Troll during the fall and related rebound, one can calculate the change in
momentum.  In this experiment, the impulse comes out 30% higher than the
change in momentum.  I have gone through the experiment several times and
cannot account for such a large difference.  The impulse curve generated
is very symmetrical and consistent.  The Troll I am using has a mass of
0.23 kg placing a good force on the probe as it falls 73 cm (using
center-of-mass measurements).  I have the probe locked down quite well so
as to reduce vibrations.  I have calibrated the probe several times
thinking that might be a problem.  Any suggestions?  The impulse is
consistently 30% - 35% higher than the change in momentum.

Lowell Herr
Project PHYSLab
The Catlin Gabel School
Portland, OR 97225