Measuring the Added Mass of a Falling Coffee Filter

Author / Creator

AAPT SM21 (2021)

Conferences

AAPT SM21 PS.D-SU-03: Introductory Labs/Apparatus II (2021)

Available as

Online

Summary

The acceleration of a falling coffee filter released from rest is always much less than the free-fall acceleration of gravity, g. This is true even near the initial release, when the part of the dr...

The acceleration of a falling coffee filter released from rest is always much less than the free-fall acceleration of gravity, g. This is true even near the initial release, when the part of the drag force proportional to the velocity is negligible. This small acceleration occurs because there is a part of the drag force that is proportional to the acceleration. This part is called the added mass. The added mass is a large effect for falling coffee filters. Nesting the coffee filters does not change the added mass. The measured value of the added mass from the initial acceleration agrees with the theoretical value calculated for an ideal fluid. In experiments using a motion sensor or video analysis, it is easy to measure both the added mass and the steady-state drag force.

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