Verlet Integration

It would be interesting to see another version of the Particle physics system that uses Verlet integration to animate objects' speed and acceleration, and to discuss the advantages / disadvantages compared to the Euler Integration scheme that you've already demonstrated. Verlet integration models tend to be much more stable, and realistic (under many conditions).

Start with the existing Particle physics system and its demonstrated Euler Integration scheme, since no file or test is named in the issue. Define a Verlet-based version and document the advantages and disadvantages compared with Euler integration; done means the alternative animation and comparison are both presented.

Written by the indexing model from the issue text.