how can we use statistical mechanics to find the probability of a particle inside a sphere to escape through a hole on the surface (no potential energy) ? any ideas ??
I don't think this is statistical mechanics. Just compare the area of the hole to the area of the sphere, and consider how fast the particle is moving.
Probability of particle traveling at speed U escaping from volume V through aperture area A in time period dT will be proportional to U.A.dT/V. Don't know what the multiplicative constant would be - perhaps depends on geometry.