The drag force is an important fact of life for the small marine crustaceans cal

Question

The drag force is an important fact of life for the small marine crustaceans called copepods. The drag force for small objects in water is very different from the drag force in air, so the drag equations of this chapter don't apply. However, we can estimate the drag force from data. The velocity graph of (Figure 1) shows two phases of the swimming motion of a 2.2 mg copepod. First it swims vigorously, speeding up; then it slows down under the influence of drag.

a) What is the magnitude of the drag force?

Explanation / Answer

a = dv/dt

a = -.70/.20 = -3.5 m/s^2

F = ma

F = 2.2 x 10^-6 kg * -3.5 = 7.7 x 10^-6 N

(b )

D/w = 3.5 / 9.8 = 0.36

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