PM is considered an obsolete method as it does not model close interaction between particles well.

The water you have added at this point is not "free" to lubricate flow between particles.

There are two ways in which one might distinguish between particles.

The distinction between these and other particles can be difficult for learners to grasp.

In this case the pores are gaps between very small particles.

In particular, the force law between charged particles is affected.

The same relationship exists between particles and information when we come to talk about the velocity of light in general.

This law holds no matter how complicated the force is between particles.

The distance between particles is so great that they would never collide with each other.

Is there a difference in the strength of the interaction between particles here?