A fan’s blades rotate
The movement of any body or object can be classified as translation, rotation or a combination of the two.
In translational motion , all points on the object follow parallel paths and have the same velocity. In this case, we can treat this object as a point, or rather, as a point object. To analyze its motion, we can apply the equations of uniformly rectilinear motion and also the equations of uniformly varied rectilinear motion. An example of translational motion is that of an elevator. It goes up and down, but has no rotation, so at any given instant, all points on the elevator have the same speed.
In the rotation motion , all points of the object follow circular paths with the same angular velocity. Typically, the description of rotational motion is done with the equations of uniform circular motion and circular motion with constant acceleration. The blades of a fan rotate: all points on the blades have the same angular velocity.
The motion of an airplane’s propeller in flight is combined. It rotates around its axis, in addition to having a translational movement, moving forward at the same speed as the device.
The analysis of this movement can be done by considering, separately, the movement of the central point of the propeller, which moves forward along with the plane; and the rotational movement of its blades, as seen by the pilot. Thus, we can calculate, for a given instant, both the position of the central point of the propeller and the angular position of each of the blades.
Combining these two results, we can plot the trajectory from any point on the helix, which results in a helical trajectory to any point other than the central point, which describes a rectilinear trajectory.