Math Insight

Quiz 8

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  1. A molecule is diffusing in one-dimension with diffusion coefficient $D=0.0084$ $\frac{mm^2}{s}$. Assuming a molecule's position cannot go negative, how long, on average, will it take the molecule to diffuse from $x=0$ to $x=0.073$ mm?
    seconds.

  2. Let $c(x,t)$ be the concentration of a molecule at position $x$ and time $t$. The concentration of a molecule at time $t=9$ ms is $c(x,9)= 2 x^{2} + 4 x + 2$ molecules per mm. If the molecules are diffusing with diffusion coefficient $D=0.009$ $\frac{mm^2}{s}$, what is the flux $J$ at time $t=9$ ms?

    $J(x,9) = $
    $\frac{mm^2}{s}$.