How Does Box Size Affect Kinetic Energy Calculations in Gas Molecules?

[majid_mahjoori]

In definition and proof of kinetic energy, it uses the second law of Newton. The length of the box is L and it uses this length to define the time of applying the force on the wall. Actually this time should be only time that molecule reaches to the wall and changes its velocity.

My question is:

is this length of box is considered as small as the size of force field of the Atom or Molecule?

 

[mfb]

Which box?

I think there is some context missing.