If a molecule, with radius r, averages n collisions as it travels distance L, then the average distance between collisions is L/n, and is called the mean free path λ, .
The mean free path is independent of temperature.
The mean time between collisions is temperature dependent.
Assumptions for ideal gas:
- # of molecules N is large
- They obey Newton’s laws
- Short-range interactions with elastic collisions
- Elastic collisions with walls (an impulse…..pressure)
- What we call temperature T is a direct measure of the average translational kinetic energy
- What we call pressure p is a direct measure of the number density of molecules, and how fast they are moving (vrms)