Air molecules are indeed in constant random motion due to their kinetic energy. This motion is what we refer to as "thermal motion" or "Brownian motion." While air molecules move randomly in all directions, their collective behavior follows the principles of fluid dynamics and gas laws, which explain why air flows in a particular direction when subjected to pressure differences.
When air enters a vacuum cleaner's hose, it does so because of the pressure difference between the inside and outside of the hose. Inside the vacuum cleaner, a motor-driven fan creates an area of lower pressure, effectively creating a partial vacuum. Meanwhile, the atmospheric pressure outside the hose is relatively higher. Nature tends to seek equilibrium, so air flows from regions of higher pressure to regions of lower pressure.
The flow of air into the vacuum cleaner's hose is a direct consequence of this pressure gradient. The air molecules move randomly, but those moving in the direction of the hose (toward the lower pressure region) outnumber those moving in the opposite direction (away from the hose). As a result, there is a net movement of air into the hose, which we perceive as suction.
Once inside the vacuum cleaner, the air continues to flow due to the design of the machine's internal components, such as filters and exhaust systems. These components help maintain the pressure difference and guide the air through the cleaning process, collecting dust and debris along the way.
So, it's not that the air "knows" to go down the vacuum cleaner's hose; rather, it follows the principles of fluid dynamics and gas laws driven by the pressure difference between the inside and outside of the vacuum cleaner. The concept is similar to how wind blows from areas of high pressure to areas of low pressure, creating airflow and weather patterns in the Earth's atmosphere.