phys 369 09 hw 9 revised c

# phys 369 09 hw 9 revised c - Phys. 369, Fall 2009 Homework...

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Phys. 369, Fall 2009 Homework #9 - Revised c (same as b except for extra help on problem 3) Due: Fri. Nov. 13, beginning of class 100 points total 1. (14 points) Suppose that you have a sample of fused silica beads with a diameter of exactly 0.500 microns. Suppose that you wish to measure the Brownian motion of these beads while suspended in water at a room temperature. Water has a viscosity η = 0.010 g cm 1 s 1 . a) Go to http://wien.cs.jhu.edu/AnnusMirabilis/index.html#common and navigate your way from there to an English translation of Einstein’s 1905 paper “Investigations on the theory of the Brownian movement.” Eq. (7) of that paper gives an expression for the diffusion constant D of a small sphere embedded in a fluid of known viscosity and temperature. Read back through the preceding pages until you understand the meaning of each symbol in eq. (7). Rewrite eq. (7) using the notation of the book section by Tipler. Also, read the section “FORMULA FOR THE MEAN DISPLACEMENT OF SUSPENDED PARTICLES. A NEW METHOD OF DETERMINING THE REAL SIZE OF THE ATOM” on the last two pages. This section gives the key result of the paper. You do not need to understand Einstein’s method of derivation of this result, since it is much more difficult to follow than Langevin’s method, reproduced in the book section by Tipler.

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## This note was uploaded on 11/06/2010 for the course PHY 369 taught by Professor Staff during the Fall '08 term at University of Texas at Austin.

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phys 369 09 hw 9 revised c - Phys. 369, Fall 2009 Homework...

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