Eddy viscosity is proportional to the square of one value of this quantity in a model named for it developed by Prandtl. The square root of little g times one value of this quantity appears in the denominator of the Froude number that models ship behavior. Ballistic electrons have a large value of one form of this quantity relative to the surrounding material. The ratio between two characteristic values of this quantity defines the (*) Knudsen number and determines if continuum mechanics apply. This quantity times dynamic viscosity over kinematic (-5[1])viscosity defines the Reynolds number. The average value of this quantity between (10[1])collisions in a gas is the mean free path. For 10 points, the volume of fluid inside a pipe equals cross-sectional area times what quantity with units of meters? (10[3])■END■