What is Stoke’s law in physics?
the law that the force that retards a sphere moving through a viscous fluid is directly proportional to the velocity of the sphere, the radius of the sphere, and the viscosity of the fluid. the law that the frequency of luminescence induced by radiation is usually less than the frequency of the radiation.
What is Stokes law used for?
Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes’ law can be used to calculate the viscosity of the fluid. A series of steel ball bearings of different diameters are normally used in the classic experiment to improve the accuracy of the calculation.
What is the equation for Stokes law?
It was done in the 1840’s by Sir George Gabriel Stokes. He found what has become known as Stokes’ Law: the drag force F on a sphere of radius a moving through a fluid of viscosity η at speed v is given by: F=6πaηv. Note that this drag force is directly proportional to the radius.
What are the four conditions of Stokes law?
1) The law applies to a fluid of infinite extent . 2) The law does not hold good if the spherical body is moving so fast that conditions are not streamline. 3) The spherical body must be rigid and smooth .
What is unit of viscosity?
The SI unit for dynamic viscosity η is the Pascal-second (Pa-s), which corresponds to the force (N) per unit area (m2) divided by the rate of shear (s-1). Just as in the definition of viscosity!
How is viscosity calculated?
There are several formulas and equations to calculate viscosity, the most common of which is Viscosity = (2 x (ball density – liquid density) x g x a^2) ÷ (9 x v), where g = acceleration due to gravity = 9.8 m/s^2, a = radius of ball bearing, and v = velocity of ball bearing through liquid.
What is the law of viscosity?
Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity.
What is Stokes law and terminal velocity?
Stokes’ law shows that the frictional drag (F) is directly proportional to the weight of the sphere; in other words F is proportional to r3. The formula for viscosity shows that the terminal velocity (v) is proportional to the radius squared; v is greater for a larger sphere than for a smaller one of the same material.
What are the limitations of Stokes law?
When the solid content of a suspension is high, Stokes’ equation may not show the real sedimentation rate. High solid content imparts additional viscosity to the system, which must be taken into consideration if the correct rate of settling is to be determined. The equation contains only the viscosity of the medium.
What is the formula for terminal velocity?
Solving for Terminal Velocity. Use the terminal velocity formula, v = the square root of ((2*m*g)/(ρ*A*C)). Plug the following values into that formula to solve for v, terminal velocity. g = the acceleration due to gravity.
What is the viscosity of water?
The dynamic viscosity of water is 8.90 × 10−4 Pa·s or 8.90 × 10−3 dyn·s/cm2 or 0.890 cP at about 25 °C. Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C.
What is critical velocity?
: the greatest velocity with which a fluid can flow through a given conduit without becoming turbulent.
What is the viscous force?
A measure of a fluid’s resistance to flow. Viscous forces in a fluid are proportional to the rate at which the fluid velocity is changing in space; the proportionality constant is the viscosity.