Atoms having the same velocity $v$ in modulus simultaneously fly into the cylinder through a small hole located in the center of the bottom of the cylinder. The directions of atomic velocities are distributed uniformly inside the cone with a small angle $\Delta$ at the vertex. The velocity cone is aligned with the cylinder. Radius of the cylinder $R$, its height $H$. Estimate the time of uniform filling of the space inside the cylinder with atoms in the case of elastic reflection of atoms from its wall and in the case when, after the time $t \gg \frac{R}{v}$,$\frac{H}{v}$ after hitting the wall, the atom moves inside the cylinder at any angle to its wall at a speed $v$.
