Magnus Effect in Classroom: A New Low Cost Physics Lab

We consider a simple experiment, in which a paper cylinder rolls down an inclined ramp and falls off the edge of a table. If the cylinder is sufficiently light, the effects of the Magnus force on it will be visible, with its trajectory curving back below the edge of the table, instead of the usual parabolic path for a point mass. We construct a mathematical model that relates the density of air (among other physical quantities) to the vertical position of the cylinder when its horizontal displacement from the edge is maximum. Thus, with only a high-speed smartphone camera that captures the motion of the cylinder and any video analyzing tool, the air density in the classroom can be estimated.