2C30.65 Coffee Filter Drag


Terminal velocity and the velocity dependence of the drag force


Coffee filters are dropped singly and nested together, and from various heights. The velocity and acceleration of the filters are measured.



  • Coffee filters
  • (Optional) [1] Metre stick
  • (Optional) Venier software motion sensor and MacMotion running on a PC

Important Notes

  • A string was hung from the ceiling above the motion sensor to provide a guide for dropping the filters. The filters, especially the single filter, had a tendency to flutter


  1. Drop a single coffee filter. Note its motion.
  2. Drop two filters nested together. Compare their motion to the single coffee filter.
  3. Drop the single filter from a height of 1 meter. Ask the students to guess from what height the nested filters should be dropped for them to reach the ground at the same time as the single filter dropped at 1 meter. It turns out that this height is very close to 1.4 meters, suggesting that the drag force in this case goes as the velocity squared.
  4. (Optional) Measure the velocity of the filters using the Vernier software motion sensor and MacMotion.


Additional Resources


  • PIRA 2C30.65
  • DaR M-136; Ehrlich(2) 2.13 p 40
  • Angell, Carl and Trond Ekern, "Measuring Friction on Falling Muffin Cups" TPT 37(3), 181-2 (March 1999)


  • Don't attempt this at home!

Last revised

  • 2018


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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.