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A smartphone magnetometer is used to record the magnetic field of a freely falling point dipole magnet. The recorded magnetic field vs. time data are analyzed in accordance with the spatial dependence of the magnetic field to calculate the acceleration due to gravity g. The experiment gives local g to be 9.79 ± 1.9% m/s[superscript 2].

A phone emitting sound of a fixed frequency is sliding on an inclined plane and approaching a second phone kept at the bottom of the plane. The detected frequency versus time data by the second phone are used to calculate the acceleration of the sliding phone. The primary objective of this paper is to calculate the sliding friction between the phone and the plane from the acceleration values. It demonstrates that the sliding friction is constant irrespective of the inclination of the plane. Results are in good agreement with the one obtained from the video analysis.

The one-dimensional finite well is a textbook problem. We propose approximate approaches to obtain the energy levels of the well. The finite well is also encountered in semiconductor heterostructures where the carrier mass inside the well (m[subscript i]) is taken to be distinct from mass outside (m[subscript o]). A relevant parameter is the mass discontinuity ratio beta = m[subscript i]/m[subscript o]. To correctly account for the mass discontinuity, we apply the BenDaniel-Duke boundary condition. We obtain approximate solutions for two cases: when the well is shallow and when the well is deep. We compare the approximate results with the exact results and find that higher-order approximations are quite robust. For the shallow case, the approximate solution can be expressed in terms of a dimensionless parameter sigma[subscript l] = 2m[subscript o]V[subscript 0]L[superscript 2]/h-bar [superscript 2] (or sigma = beta[superscript 2]sigma[subscript l] for the deep case). We show that the lowest-order results are related by a duality transform. We also discuss how the energy upscales with "L" (E is proportional to 1/L[superscript gamma]) and obtain the exponent gamma. Exponent gamma [right arrow] 2 when the well is sufficiently deep and beta [right arrow] 1. The ratio of the masses dictates the physics. Our presentation is pedagogical and should be useful to students on a first course on elementary quantum mechanics or low-dimensional semiconductors. (Contains 2 tables, 3 footnotes and 4 figures.)

Describes a study that examined the effectiveness of eight search engines for the World Wide Web. Calculated traditional information-retrieval measures of recall and precision at varying numbers of retrieved documents to use as the bases for statistical comparisons of retrieval effectiveness. Also examined the overlap between search engines. (Author/LRW)

Kinematic models are often very useful. The back and forth throw of a ball between two ice skaters may help us appreciate the meson exchange theory of Yukawa. If the skaters throw the balls at each other, they move backward, which is equivalent to a repulsive force between them. On the other hand, if they snatch the ball from each other, the result will be akin to an equivalent attractive force between them. Such illustrative models may help us understand advanced concepts.