re brownian motion

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From: Ronald Wong (ronwong@inreach.com)
Date: Thu Feb 12 2004 - 00:53:21 PST 

Message-Id: <l03102804bc50e2e77f26@[209.209.18.113]>
Date: Thu, 12 Feb 2004 00:53:21 -0800
From: Ronald Wong <ronwong@inreach.com>
Subject: re brownian motion

Jerry asked:

>What provides the energy for Brownian Motion to work?

Jerry:

The Brownian Motion involves the random motion of small particles in a
fluid (pollen grains in water, smoke particles in air, etc.).

Since the fluid is above 0° K, it's molecules move about in every which
direction with a kinetic energy that is dependent on the temperature of the
fluid.

   For instance, in the case of a gas, the kinetic energy
   is directly proportional to the absolute temperature
   (Kelvin or Rankin) of the gas.

Anytime these particles collide with something - another water/air
molecule, a particle of smoke or a grain of pollen - there is an exchange
of momentum and energy.

The energy for the visible grain of pollen (or smoke particle) that you
are referring to comes from collisions with the invisible molecules of the
fluid.

Everyone seems to want to post applets on the WWW that portray this
phenomena. A typical example is:

http://www.phys.virginia.edu/classes/109N/more_stuff/Applets/brownian/brownian.h
tml

Enjoy.

ron

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