BE 112A
BIOMECHANICS
W 2010
Homework #1
Due Wednesday 1/13, 5:00 PM
before class
No late submissions
Reading Assignment
:
A short history of Biomechanics and its basic method of approach:
Chapters 1.1 to 1.7 of the text.
Study and Exercise Assignment
:
1.
One of the most useful results in science is
Stokes Formula
for the force F on a sphere with radius a
moving with velocity U in a viscous fluid with coefficient of viscosity μ at very low Reynolds number:
F = 6 π µ a U.
This solution was obtained by George Stokes.
He solved the “Stokes approximation” of the equation of
motion for a Newtonian fluid moving at very low Reynolds number (i.e. he neglected inertial forces and also
body forces).
It assumes the s
phere is moving in an “infinite” volume, i.e. the walls of the fluid container
are far from the surface of the sphere.
Derive this formula from the traction distribution on the surface of the sphere (listed in problem 4.3 of the
First Course, page 104).
How would you use this formula to estimate the radius of a macromolecule, e.g. albumin ?
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 Winter '08
 PeterChen
 George Stokes, newtonian viscous fluid, low reynolds number

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