david lang wrote:
Andrew Gabriel wrote:

That's what "suction power" is -- the vacuum pressure multiplied by
the air flow. Neither the vacuum nor the airflow are meaningful by
themselves -- a vacuum pump and a large desk fan would have better
individual ratings than a vacuum cleaner, but are useless at cleaning
floors.

In practice you cant have vacuum pressure and airflow at the same time.

As the other poster has suggested, real physics are more complex

Basically, pressure differences cause airflow.
In the case of an absolute vacuum, if you have a hole with a vacuum on
one side, then the air will enter it at about the speed of sound.

Usually vacuum cleaners don't suck quite so hard.

When you partially obstruct the hose of the vacuum, then if the vacuum
inside remains the same, the airflow drops.

Take the insides out of a ballpoint pen, and play with obstructing the
end with your finger, while sucking.


In practice, the vacuum cleaner pump has a curved performance graph.
If you were to plot the pressure drop it's working against with airflow,
it starts off at zero pressure drop at the maximum airflow, and drops
to zero airflow at some pressure drop at which the pump can't do any more.