In a recent paper (Robinson G and Robinson I 2013 Phys. Scr. 88 018101) the authors developed the differential equations which govern the motion of a spherical projectile rotating about an arbitrary axis in the presence of an arbitrary wind, assuming that both the drag force and the lift force are independent of the Reynolds number and proportional to the square of the projectile's velocity. In this paper, by dimensional analysis, the latter assumption is shown to be incorrect for forces dependent on the angular velocity of the projectile, e.g. the lift force.