The article considers a mathematical model of the movement of single particles along the inclined shelves of pneumatic separators. It is noted that in the practice of such analytical calculations, the force of aerodynamic resistance of the airflow to the movement of particles along an inclined plane is considered negligible compared to the friction force on the shelf surface. The results of simulation experiments for calculating the final velocity of particles falling off the shelf with varying values of their sizes and coefficient of friction are analyzed. The substantiation of the consideration of the aerodynamic drag force is carried out to describe the movement of particles in separators not only in free flow, but also when they move along inclined shelves. It is concluded that for engineering calculations, the aerodynamic resistance of the medium can be neglected only for particles larger than a certain size.