posted by Jack on .
Determine the units of viscosity,m, in the following equation:
t=m(du/dy), where t is a shear stress, u a velocity, and y is a distance in (a) the Engineering English system, and (b) the SI system.
stress is force/area = kg-m/s^2m^2 = kg/ms^2
I'll use v distinguish viscosity from mass
kg/ms^2 = v * (m/s / m) = v/s
v = kg/ms or kilograms per meter-second
this can be verified at wikipedia under the viscosity article.
looks like t = kg * (m/s / s) = kg m/s^2 = Newtons
Steve is correct.
In my generation, viscosity was usually quoted in Handbooks in units of g/(cm*s), called the poise, or 1% of that, called the centipoise.
English units of viscosity were seldom used. I seem to recall some English units called Saybolt slugs. I have never heard a better argument for the metric system.
A sensible unit of viscosity in the English engineering system would be slugs per foot-second.