The Equivalence Principle and the Dynamics of an Accelerated Helium-Filled Balloon

Abstract

In an interesting recent article, V. M. Aguilella et al. (Phys. Teach. 40, 214–216 (April 2002) analyzed the dynamics of a helium-filled balloon tied by a string to the seat of a car that is moving at constant speed in a horizontal curve. To achieve their goal, the authors carefully apply Newton's laws of motion to a situation involving a noninertial frame of reference. This note, whose purpose is twofold, is meant to complement the article by Aguilella and his colleagues.