A simple demonstration of Einstein's lift: a body thrown upwards moves rectilinearly and uniformly relative to a free-falling model of the lift

Abstract

The educational model of Einsteinʼs lift consists of a table suspended from an electromagnet. A flexible support is attached to the table. A metal ball is on the support and deforms it. When the electromagnet is deenergized, the table falls, the system goes to a weightless state and the support throws the ball up. A camera carries out frame-by-frame photography of the free-falling model. The resulting photographs are imported into a computer, projected on to a screen with a multimedia projector and analyzed in a lecture with the audience. The experiment proves that a thrown up body moves rectilinearly and uniformly relative to the free-falling model of Einsteinʼs lift. In the second version of the experiment we replace the ball with a water drop lying on the unwettable surface of the table of the model.

Three experiments on the Einstein’s lift

“…In the background of Galilean relativity student difficulties with inertial frames of reference have been documented [3][4][5] and considering different frames of references in a given problem sometimes is difficult for students [6]. Researchers have observed that these topics can be more effectively understood if students perform experiments, carry out data acquisitions and quantitative analysis, and actually see a phenomenon in different frames of reference [6,7].…”

“…In a recent paper [7] the authors presented an educational model of Einstein's lift. In that model of lift, an elastic sheet was deformed by a small sphere when the lift is at rest.…”

“…In this paper we propose three experiments occurring in Einstein's lift, adding to the springmass system, analogous to the one proposed in reference [7], the two repelling magnets system and the pendulum oscillations in free fall. The experiments, based on video acquired with a camera or with a common smartphone, were easily quantitatively analysed by undergraduate students thanks to Tracker in both the inertial and moving frames of reference.…”

A teaching-learning sequence to present the relativity principle and the principle of equivalence in classical Mechanics to pre-service physics teachers

“…Student difficulties with inertial reference frames and relative motion have been documented in some papers in the past [1][2] while more recently students' understanding of the PoE and RP was also investigated [4][5]. According to some authors, learning effectiveness can be improved when students are allowed to see a movement in different frames of reference and perform the experiments independently while carrying out quantitative estimates.…”

“…Although there are some "good" educational experiments, few are available for inexpert students while most require that students and teachers have advanced experimental skills. Many experiments were focused on demonstration of Einstein's lift [5,6] and on the physics of free fall, as the ones illustrated in ref [7] where the author reported a collection of experiments by employing techniques that can be implemented by unskilled students. These experiments integrate new technologies such as smartphones and free software (Tracker®) for video analysis.…”