1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Brownian Motion problem

  1. Nov 17, 2006 #1
    In one of my hw problems it is a problem under the section of Brownian motion. It asks me to compute the average velocity of particles!

    here is the exact problem:

    The average speed of hydrogen molecules at 0 degrees C' is 1694 m/s. Compute the average speed of colloidal particles of "molecular weight" 3.2*10^6 g/mol.

    -What I know about the problem is that the formula for avrg speed is 1.59*sqrt(kT/m), where k is the boltzmann constant! I do not understand why so much information is given? How can I convert molecular weight into simple mass? The ans is also 1.3 m/s, but i have no idea how to arrive at it, please help!! I would show more work, but I am not really getting anywhere so far
    Last edited: Nov 17, 2006
  2. jcsd
  3. Nov 17, 2006 #2
    The equipartition of energy principle requires that the KE when there is Brownian motion is 1/2kT. So if I set up the equation such that 1/2kT=1/2mv^2, am i on the right track?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook