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F = ma (11–17)
Dimensional Analysis
FMA-2024-15 · 2024 F = ma (AAPT)

2024 F = ma Exam — Question 15

The viscous force between two plates of area A, with relative speed v and separation d, is F = ηAv/d, where η is the viscosity. In fluid mechanics, the Ohnesorge number is a dimensionless number proportional to η which characterizes the importance of viscous forces, in a drop of fluid of density ρ, surface tension γ, and length scale ℓ. Which of the following could be the definition of the Ohnesorge number? ηℓ
Source: Question 15, 2024 F = ma Exam, © 2024 American Association of Physics Teachers (AAPT) and the U.S. Physics Team. Adapted by PhysicsTrainer: reformatted into a separate question and answer choices for online multiple-choice practice; any shared setup from nearby questions is repeated here. Not affiliated with or endorsed by AAPT or the U.S. Physics Team.