 # Stokes Law Calculator

Stoke's law states that at low velocities the frictional force on a spherical body moving through a fluid at constant velocity is equal to 6 π times the product of the velocity, the fluid viscosity, and the radius of the sphere. In short, a sphere moving through a viscous fluid is directly proportional to the velocity of the sphere as well as the radius of the sphere, and the viscosity of the fluid.

Stokes Law Calculator

m/s2
m
kg/m4
kg/m3
kg/m-s
m/s

Formula

Fall or Settling Velocity :
Vt = gd2 (ρp - ρm)/18μ

Acceleration of Gravity :
g= 18 μ Vt /d2p - ρm)

Particle Diameter :
d= √18 μ Vt /g (ρp - ρm)

Density of Medium :
ρm = ρp - 18 μ Vt/ d2

Particle Density :
ρp = 18 μ Vt /d2+ ρm

Viscosity of Medium :
μ = gd2( ρp - ρm)/18 Vt

Where,
Vt = Fall or Settling Velocity,
g = Acceleration of Gravity,
d = Particle Diameter,
ρm = Density of Medium,
ρp = Particle Density,
μ = Viscosity of Medium.

Stoke's Law is defined as the basis of the falling - sphere viscometer. In the viscometer the fluid is stationary in a vertical glass tube. This online Stokes Law Calculator is useful in calculating various parameters of fluid in viscometer.

Example:
Calculate the fall or settling velocity (Vt) for the given details through Stoke's Law formula.
Acceleration of Gravity (g) = 25 m/s2
Particle Diameter (d) = 15 m
Density of Medium (ρm) = 5 kg/m4
Particle Density (ρp) = 10 kg/m3
Viscosity of Medium (μ) = 20 kg/m-s

Solution:
Apply formula:
Vt = gd2 (ρp - ρm)/18μ
t= 25*15 (10-5)/18*20
Fall or Settling Velocity (Vt) = 78.13 m/s