Magnetic Force from Terminal Velocity

In a traditional teaching approach, a physics course begins with mechanics, and generally the braking effect due to magnetic interactions is not mentioned among the various types of friction presented (static, sliding, rolling) because students will discover magnetism only in later chapters. In our didactic experience this traditional choice is only partially effective for two reasons. First of all it does not distinguish between the nature of the interactions involved in friction processes and the way in which their effects appear, allowing students to believe erroneously, for example, that sliding friction (due ultimately to electrical interactions) is intrinsically “more mechanical” than the braking force produced by magnets moving over a metal surface. Secondly, the traditional approach doesn’t consider that Newtonian dynamics is sufficient to get a quantitative albeit empirical description of a magnetic braking force, without any introduction to magnetism, exactly as it is traditionally done, for example, for sliding friction, described as a force without discussing its complex electrical nature.