22. Answer: 10.

Analysis: From $\mathrm{AB}^{2}=A 0^{2}+O B^{2}=20^{2}+15^{2}=25^{2}$, we know that the length of the connecting rod is 25 centimeters. When slider $\mathrm{A}$ slides down to point 0, the distance of slider $\mathrm{B}$ from point 0 is 25 centimeters, so slider B has moved $25-15=10$ (centimeters).
The two sliders $\mathrm{A}, \mathrm{B}$ in the right figure are connected by a rod and can slide on vertical and horizontal tracks, respectively. Initially, slider $\mathrm{A}$ is 20 cm from point 0, and slider B is 15 cm from point 0. Question: When slider $\mathrm{A}$ slides down to point 0, how many centimeters has slider $\mathrm{B}$ moved?