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I am answering some exercises in thermodynamics, and I am still in trouble with some values and constants. In the exercise, it is given: $\mu_\text{air}=1.8\cdot10^{-5}~\text{kg/m s}$. What for is this value used? In the case, I need to find some tensions in given points, and I know the speed profile of the air.

Other question: As I need the tension in some points, and it is about air, is it the same thing as pressure?

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$\mu$ is the dynamic viscosity. The wall shear stress is a force (per unit area) on the wall by the fluid, which has units of $Pa$. So, the velocity profile AND the viscosity together will give you a tension (see second link).

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Thank you! It helped a lot! –  Ataias Reis Apr 22 '13 at 9:38
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