Question

Our molecular model of matter describes a fluid as consisting of lots of little particles (atoms or molecules)

moving around very fast. Collisions between the molecules makes the particles of the fluid change directions and speeds often and randomly. We've talked about two different phenomena that depend on these random molecular interactions: viscosity and diffusion. Viscosity is the way collisions with other parts of the fluid slow down faster-moving bits of fluid, and diffusion is the way collisions spread out concentrations of molecules. Let's consider how the viscosity and diffusion coefficients might depend on the properties of the fluid by dimensional analysis

Part A
What are the units of viscosity, in base SI units (kg, m, s)?

Part B
What are the units of the diffusion coefficient, in base SI units (kg, m, s)?

Answer 1

a) μ = [kg / m s]

b) D = m²/s

Step-by-step explanation:

Viscosity is equivalent to a friction force that opposes the movement of fluids, it is defined by the relation

Shear stress = μ speed gradient

Fr/A = μ v₀ / h

Where Fr is the shear force, A the area, h the height and v₀ the velocity of the fluid layer

μ = [kg / m s]

The diffusion coefficient characterizes the ability of a material to move in a given solvent, depending on the size of the solute, the viscosity of the solvent, temperature

J = - D dΘ / dx

J is the broadcast glare

D = [m² / s]