Research Papers in Physics and Astronomy


Date of this Version

March 1997


Published in THE PHYSICS TEACHER VOL. 35, MARCH 1997. Copyright 1997. Used by permission.


What analyst would have predicted that Mr. CoffeeTM would diversify into the scientific supplies market? Nevertheless, that coffeemaker's filters, with their flat bottoms and fluted sides, have been popular in physics classroom experiments for some time now. Besides being cheap and readily available, coffee filters allow students to work experimentally with non-constant forces and, because the filters can be easily stacked without changing their aerodynamic profile, the variation in drag force with velocity can be studied. Since stacks of a few filters fall at speeds of about a meter per second and even a stack of ten reaches terminal velocity rapidly, they can be observed with no more equipment than a stopwatch and meterstick. However, for those who prefer more high-tech approaches, the filters can be dropped directly onto sonic rangers and the data imported to a computer, or the filters can be videotaped and their motion digitized and analyzed using software developed for just such purposes.

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