4 ms·
> the airflow indeed also pushes the brass disk forward The force on the disk is caused by an opposite force on the fan blades, cancelling them out (since they
by perilunar 6y ago
> the airflow indeed also pushes the brass disk forward
The force on the disk is caused by an opposite force on the fan blades, cancelling them out (since they are connected by the frame and the bearings), so it cannot cause the fan to rotate.
The rotation is due simply to unbalanced thrust from the fan. The unimpeded side produces more thrust than the impeded side, so the fan turns to that side.