An acrylic tube containing a metal washer and a feather
is inverted to show that air resistance slows the feather but not the washer.
Then the tube is evacuated, and inverted again to prove that it is air resistance
- not the fact that the feather is lighter - that causes the objects to
fall at different rates.
This demo can be found in cabinet B on shelf 2 of the UCSD PUL Demo Room
(WLH 2015).