A magnetic set-up to help teach Newton’s laws

Abstract

A set-up comprising a magnetic disc, a solenoid and a mechanical balance was used to teach first-year physics students Newton's third law with the help of a free body diagram. The image of a floating magnet immobilized by the solenoid's repulsive force should help dispel a common misconception of students as regards the first law: that stationary objects are not being acted on by any force at all. Dropping the magnet onto the electrified solenoid, which can change polarity, can lead to more sophisticated elaboration of the second law.

A simple and effective magnetic dynamometer to teach Newton’s third law

“…Other important applica tions of the third law involve collisions where momentum and energy conservation concepts are P a P e r A simple and effective magnetic dynamometer to teach Newton's third law explored [11]. A very feasible way to exchange forces between objects is by means of magnetic fields, since they avoid the mechanical contact of the objects and their magnitudes can be con trolled by electric current in solenoids or varying distances between permanent magnets [12][13][14]. A remarkable experiment involves the fall of magnets that reach terminal speed inside elec tric conductive tubes, exchanging forces between them via magnetic fields generated by eddy cur rents [15,16].…”

“…A remarkable experiment involves the fall of magnets that reach terminal speed inside elec tric conductive tubes, exchanging forces between them via magnetic fields generated by eddy cur rents [15,16]. Some approaches use familiar objects, like weights and scales, while others use more involved apparatus like frictionless bead tables [11], currentcontrolled solenoids [13,14], digital force probes [12] and Arduino boards [10], just to cite a few. Despite their ability to explore different aspects of the third law, we feel the lack of a proposal that uses really cheap materials and that shows in a very direct way the qualitative and quantitative aspects.…”