# What is Stokes law: Definition and 20 Discussions

In 1851, George Gabriel Stokes derived an expression, now known as Stokes law, for the frictional force – also called drag force – exerted on spherical objects with very small Reynolds numbers in a viscous fluid. Stokes' law is derived by solving the Stokes flow limit for small Reynolds numbers of the Navier–Stokes equations.

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1. ### A Integrating the Stokeslet: Solving Expression 7 from ResearchGate Publication

https://www.researchgate.net/publication/301874096_Emergent_behavior_in_active_colloids/link/5730bb3608ae08415e6a7c0a/download (expression 9 on this document derivation). I understand the need for substitution etc into the integral. What puzzles me is how the integral equals what it does. If...
2. ### How does the velocity of a ball change without buoyant force acting on it?

So my doubt is at the beginning of the problems hey are saying that the ball obeys stokes law and on the latter part of the question they are saying that no buoyant force is acting then how does the velocity of the ball change in the end? Also what is the use of specifying 'the ball never...
3. ### I Stoke's equation -- particle size

I want to solve stokes eq. for particle diameter in um size. Do i have to change the units to make them uniform. please help in solving the eq. by plugging these numbers. velocity= 50 mm/h Particle density= 2650 kg/m^3 Medium density= 1000 kg/m^3 viscosity = 1.002 mPa Gravity= 9.8 m/s^2
4. ### Radius of a Raindrop: Finding Mass & Volume

Homework Statement Using the viscosity of air as 1.8x10-5Pa s, and the density of water as 1x103kg m-3, find the radius of a raindrop traveling at a terminal velocity of 7.05ms-1. Assume Stokes law can be used. The problem is finding the density of air, I could use F = 6rvπη but I don't know...
5. ### Stokes Law/Drag Force corrections?

Hi there, I have recently been experimenting with solid metal spheres being let to fall through fluids of different viscosities and have recently been introduced to the 'Ladenburg correction'. This correction multiplies the measured velocity of the sphere to obtain the 'correct' velocity used...
6. ### Modeling Deceleration of Object Towed in Water

So this is about a modelling project I'm doing. If you have an object that was being towed in water and the towing force is suddenly removed. There is a force F=1/2(density of fluid)(C constant)(A)V^2 that acts on the object. I am trying to find the distance X it will take for the object to...
7. ### Does anyone know this equation? (fluid dynamics, Stokes law)

I was doing some research into my coursework (don't worry, this isn't a real 'help!' thread) on Stokes law, and I found this equation on this forum (posted in 2010), regarding the effect of the walls of a pipe on the calculated value for viscosity when a sphere is dropped through that pipe...
8. ### Coursework help - Stokes Law equation + graphs

Homework Statement Hi there. For my A2 physics coursework I have been doing an experiment into stokes law, in which I dropped ball bearings of various diameters into a tube filled with a liquid, worked out their terminal velocities and then used Stokes Law to calculate the viscosity of the...
9. ### Find the viscosity coeffienct of glycerol, using stokes law

Homework Statement I have been given an experiment to perform, whereby I drop steel ball bearings into a glass measuring cylinder, and time how long it takes for the ball bearing to fall a set distance. From this I should be able to work out the viscosity coeffienct of the glycerol. I have...
10. ### Using Stokes law, calculate the work done along a curve

Homework Statement Using Stokes law, calculate the work done along a curve ##\Gamma ## which is defined as edge of a spherical triangle in first octant of a sphere ##x^2+y^2+z^2=R^2##. Vector field is ##\vec{F}=(z^2,x^2,y^2)##.Homework Equations Stokes law: ##\int _{\partial \Sigma...
11. ### Determining the viscosity of glycerol at 20*C using Stokes Law.

Homework Statement I used a home made falling sphere viscosimeter to obtain: terminal velocity = 0.06216 ms^-1 I used a micrometer to obtain: radius = 0.001835m and, because my value for glycerol viscosity was way off the known value of 1.495 Pa s, I decided to measure the density of the...

Hi, I am doing physics coursework on finding viscosity of fluids by dropping a marble into fluids, finding terminal velocity, then using stoke's law to find viscosity. (using density of fluid, sphere, sphere diameter etc). I have completed all the practical, now just the write up However ... I...
13. ### Stokes law - Settling velocity and rate

Homework Statement 1. A fly ash (ρ =1.8 g/mL) aerosol consists of particles averaging 13 μm in diameter and with a concentration of 800μg/m3. Use the average diameter to calculate the settling velocity (cm/s) and settling rate (μg/m/s) of the particles in air. The Stokes-Cunningham slip...
14. ### Projectile motion or stokes law

Its a while since I've done any motion calcs so I'm after some guidance. I am vertically dropping a range of materials (size 8-20 mm) into a horizontal air stream in a pipe (pipe diammeter d , ~0.3m) The horizontal air velocity in the pipe is 10 m/s The particle bulk density ranges from...
15. ### Investigating Stokes Law: Different Formulas, Different Results?

Hello all. I'm investigating a little bit about stokes law in order to understand the settling velocity of falling particles and on the net i encountered with 2 different formulas and i simply can't find the reason why they are different. every formula gives me a different answer. The 2...
16. ### Stokes' Theorem and Maxwell's Equations

Homework Statement Faraday’s Law can be written as: \oint_P \vec{E} \cdot \vec{dl} = -\frac{d}{dt}\Phi Where \Phi is the magnetic flux. Use Stokes’ theorem to obtain the equvilant Maxwell equation (i.e. Faraday’s Law in differential form). Homework Equations Stokes' Law...
17. ### Stokes Law, Viscosity. (very simple)

I'm trying to find the viscosity of some glycerol that we dropped various steel balls down using the equation: V = [2r^2 (p – σ) g] / 9η I put in these values: p = 7800 kg m-3 σ = 1200 kg m-3 g = 9.8 m s-2 And ended up with the equation. η = 129360r^2 / 9V My problem is that I...
18. D

### Discovering Stokes Law: A Guide to Understanding its Origins and Applicability

Hi - Is it possible to derive Stokes law or is it an emprirical law.? http://en.wikipedia.org/wiki/Stokes'_law I was thinking of using the Navier-Stokes equations but i don't want to start out if it impossible.. Thx.
19. ### Calculating Stokes Law: A Guide

Would anybody derive stokes law for me or show me how to do it?
20. ### Stokes Law & Parachutes: Explained

How is stokes law related to parachutes?
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