Brownian motion applet

This applet shows the dispersal of energy from a large particle to a large number of small particles. It also illustrates Brownian motion, in which the large particle moves randomly due to collisions with the smaller particles. To get a true visualization of Brownian motion you can make the small particles invisible, so that the large particle can be seen making random movements.

The applet uses an inverse square law for the force between the particles (rather than having them bounce off each other). The force constant can be made negative if required, to simulate a gravitational system.

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Comments

In my earlier applets I used systems of coupled pendulums to look for energy dispersal, and was rather surprised to find that it didn't happen. Hence I wrote this applet to find a system in which the energy dispersal does take place.

Accuracy

Such simulations tend to suffer from inaccuracies due to the time step used in the calculations. This simulation deals with this in two ways, firstly by making sure energy is conserved in close interactions of two particles, and secondly by ensuring that the total energy of the system is conserved. For more than 100 particles the applet tends not to run smoothly, and there also seems to be an effect of the large mass spitting out the smaller masses, which I don't think is very realistic.