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Juan C. Castro-Palacio

Publications and source records attributed to Juan C. Castro-Palacio.

16 recordsLinked to original sources

From Prompts to Physical Laws: A Generative AI Workflow for Engineering Physics Education

This work explores the use of generative artificial intelligence (AI) as a source of synthetic experimental content for introductory physics courses in engineering education. Using PixVerse.ai, Grok Imagine, and Pippit, three video scenarios were generated to represent distinct resistive force regimes: constant friction, linear drag, and quadratic drag. Kinematic data were extracted from the generated videos using Tracker, an open-source video analysis tool, and subsequently fitted to the corresponding analytical models through non-linear least-squares regression in Microsoft Excel. The results show good agreement between the synthetic data and the classical kinematic equations derived from Newton's Second Law. From the fitted parameters, physically meaningful quantities were recovered in each case, with values broadly consistent with those reported in the literature under the assumed conditions. A recurring observation is that the physical plausibility of the generated motion depends on the level of detail included in the text description used to generate the videos. More specific descriptions tend to produce more coherent dynamical behaviour, suggesting that the formulation of input prompts plays a relevant role in shaping the resulting physical consistency and can be regarded as an integral component of the experimental design process. The integration of generative AI, video-based motion tracking, and curve fitting provides a complete workflow that mirrors key stages of experimental practice, from model construction to quantitative validation. The proposed methodology engages students in experimental design, data acquisition, parameter estimation, and model evaluation, promoting key engineering competencies in modelling of physical models using widely available tools. Overall, the proposed methodology demonstrates the potential of generative AI to support physics education

physics.ed-ph↗

Bringing Engineering into the Physics Lab: Exploring Crank-Slider Dynamics with Smartphones

Many of the students enrolled in the calculus-based physics sequence are pursuing engineering degrees. Lab activities that have a direct connection to engineering, analyzed with the physics they have been studying, can grab students' interest and provide a real-world connection. All the better if the equipment is inexpensive and partly self-built. In addition, we wanted to use smartphones as data collection devices. Smartphones have become valuable tools for physics education because they provide an accessible and inexpensive means of experimental data acquisition through their built-in sensors. Several free applications, such as Physics Toolbox and phyphox, facilitate sensor-based data collection and analysis, making it possible to perform meaningful laboratory activities without expensive equipment. We chose to use a simple crank-slider mechanism for our activity. The crank-slider converts rotary motion into linear motion and has common applications in such things as internal combustion engines and compressors. Educational studies have shown that slider-crank mechanisms and related mechanical devices provide effective contexts for introducing engineering concepts and connecting theoretical models with practical applications. In our implementation, a rotary motor drives a disk connected by a rod to a cart moving along an air track. Students investigate the resulting motion using smartphone data acquisition and video analysis. Experimental measurements are then compared with the predictions of a mathematical model derived from the geometry of the system.

physics.ed-ph↗

Analytical and Experimental Study of a Variable-Mass Oscillator with Constant Mass Loss

We present an analytical and experimental study of a variable-mass oscillator with constant mass loss. Starting from the equation of motion of a spring-mass system whose mass decreases linearly with time, analytical solutions are obtained in terms of Bessel functions. Simple asymptotic expressions are then derived, providing explicit descriptions of the evolution of the oscillation amplitude and frequency. The analysis is extended to include viscous damping, leading to a model suitable for direct comparison with experimental observations. Experimental measurements of the oscillator acceleration were performed using a simple laboratory setup consisting of a spring-mounted container that continuously loses mass at an approximately constant rate. The theoretical predictions accurately reproduce the measured dynamics over the entire duration of the oscillation, and the massloss rates obtained from the fits are in good agreement with independent measurements. The results provide an accessible example of variable-mass dynamics and illustrate how special-function methods can yield experimentally testable predictions in advanced undergraduate mechanics.

physics.ed-ph↗

Uniform and Accelerated Circular Motion with a Smartphone: A No-Code, AI-Generated Browser Laboratory

Smartphones have become a standard measurement instrument in the physics laboratory. Their built-in accelerometers, gyroscopes, magnetometers, and cameras have been used to investigate a wide range of phenomena in mechanics, and rotational motion in particular has proven especially well-suited to smartphone-based experiments. A recurring limitation, however, is that most experiments rely on precompiled sensor apps whose interfaces cannot be tailored to a specific activity, and until recently creating customized smartphone laboratories required programming knowledge beyond what most physics teachers possess. This paper makes two connected contributions. First, we present a validated smartphone experiment for uniform circular motion (UCM) and uniformly accelerated circular motion (UACM), in which the angular velocity and the angular acceleration are obtained from two independent smartphone channels and checked against independent video analysis with Tracker.10,14 Second, we show that generative AI can serve as a no-code development tool for the physics laboratory: the browser-based application used here was produced entirely through natural-language prompting, with no manual coding, extending to rotational motion the approach we recently introduced for acoustic experiments. The emphasis is therefore not only on what is measured, but also on how the measuring instrument itself was built.

physics.ed-ph↗

Combining Physics and Mathematics Learning: A Taylor Series Analysis of an Oscillating Magnetic Field

In this work, we present a simple and low-cost experiment designed to study the oscillations of the magnetic field created by a cylindrical magnet under two different conditions: far and short distances from the magnetic sensor. A Taylor series expansion of the magnetic field function has been done to study the convergence of the polynomial series to the real field in both situations. To carry out the experiment, a small cylindrical magnet has been attached to an oscillating and well-known spring-mass system. The resulting oscillating magnetic field has been registered with the smartphone by using the magnetometer sensor. A very good agreement has been obtained between the theoretical model for the magnetic field and the experimental data collected with the sensor located near and far from a cylindrical magnet and along its longitudinal axis.

physics.ed-ph↗

Visualizing beat phenomenon between two amplitude-modulated (AM) light beams on a solar cell using smartphones

We present a new simple experimental setup for demonstrating beat phenomenon. We have combined two amplitude-modulated light beams on a solar cell using two smartphones as signal generators and a third smartphone as an oscilloscope to visualize the resulting wave beats. A very good agreement is obtained between the theoretical model and the experimental result. It is an innovative approach to bring physics experimentation to the students and discover the potential possibilities of smartphones in basic physics courses.

physics.ed-ph↗

A very low-current electromagnetic induction experiment enhanced by acoustic means

We have created a simple, portable, low-cost setup allowing the students and teachers to experiment with and discuss electromagnetic induction in a safe way, using low currents. The simplicity and portability make these activities well suited for experiments outside of the classroom, which is particularly welcome for distance learning. The setup consists of two smartphones used as signal generators, a small coil, two loudspeakers connected to the coil and a third smartphone used as an oscilloscope. We have no doubt that simple, low cost, portable experiments using engaging elements such as smartphones, sound, and music, will be attractive for secondary school and first-year university physics courses.

physics.ed-ph↗

Using a remote control to determine the infrared absorption coefficient in water

In this work, we present a simple and low cost experiment designed to determine the infrared water absorption coefficient. We used a TV remote control as a point source of infrared light. The intensity after passing the light through different heights of a water column is measured with a solar cell connected to a speaker. The recorded signal, captured with a smartphone sound recorder, provides a practical demonstration of the Beer Lambert law. The collected data were fitted to the theoretical model, obtaining a very good agreement between the value of the water absorption coefficient obtained experimentally and that reported in the literature.

physics.ed-ph↗

A diffraction approach to assess the elastic properties of a nylon string

The Youngś modulus of a nylon string has been determined experimentally by combining elasticity theory and wave optics. A diffraction experiment has been setup to determine the change in the string diameter for different tensile forces applied by means of hanging weights. A linear elasticity model has been used to calculate the Youngś modulus. A simple method has been provided which could be used as the basis of an experiment for introductory university level.

physics.ed-ph↗

Multi-trap optical tweezers based on Kinoform Silver Mean lenses

In this paper, we present the design and implementation of multi-trap optical tweezers based on new quadrifocal kinoform lenses. The phase distribution of these diffractive lenses is characterized by the Silver Mean sequence. The focusing properties of the resulting aperiodic DOEs coined Kinoform Silver Mean Lenses (KSMLs) are numerically examined. It is shown that, under monochromatic illumination, a KSML drives most of the incoming light into four single foci whose focal lengths are related to the Silver ratio. In this way, a KSML improves the diffraction efficiency of binary Fresnel Silver Mean Zone Plates. Through experimental results, the simultaneous trapping of particles in the four focal planes and their three-dimensional manipulation is demonstrated.

physics.optics↗

Visualizing acoustic levitation using COMSOL Multiphysics

We present a new virtual laboratory developed with COMSOL Multiphysics for the simulation of an acoustic levitator. Our computer application simulates the acoustic pressure field and its interaction with a set of particles. Students can interact with the system by having the possibility of changing the frequency and distance parameters between transducers in real-time. We have also developed and shared for free use the 3D printing design files for the construction of necessary components for the acoustic levitator and the instructions for its experimental implementation. The experimental results, along with the virtual laboratory, provide the students with useful tools to understand and interpret the acoustic phenomenon involved.

physics.ed-ph↗

RLC series circuit made simple and portable with smartphones

This article presents a novel method for studying RLC series circuits using two smartphones, one used as a signal generator and the other as an oscilloscope. We measure the voltage at the external resistor as a function of frequency when subjected to a sinusoidal electromotive force. The experimental results demonstrate a remarkable agreement with the theoretical curve for the voltage at the resistor and the resonance frequency, validating the accuracy of the smartphone-based setup. The experiment fills the gap in educational materials related to electrical circuits and provides a portable alternative to traditional, expensive laboratory equipment.

physics.ed-ph↗

Experimenting with RC and RL series circuits using smartphones as signal generators and oscilloscopes

Simple, portable and low-cost experiments as RC and RL series circuits are proposed to experiment with DC circuits. Very common elements are used: a few electronics components (resistors, capacitors, coils and connecting wires) and two smartphones. We consider the charging and discharging of a capacitor in the RC circuit and also that of coil in the RL circuit. Using a smartphone as an oscilloscope we observe voltages variations which are the transient response to a square signal generated in the second smartphone. These voltage variations are directly related to the electrostatic or magnetic energy stored in the circuits. The experimental data have been collected with the smartphone used as an oscilloscope and corroborated with theoretical predictions based on Kirchhoff's laws. The comparison showed differences of the order of the 1\% or less between the calculated capacitance or inductance compared to the manufacturer values. This approach which avoids the use of expensive signal generators, oscilloscopes, or any specialized hardware can be performed in less-favored contexts and even as a home assignment.

physics.ed-ph↗

Multiplexed vortex beam-based optical tweezers

The design and implementation of a multiplexed spiral phase mask in an experimental optical tweezer setup are presented. This diffractive optical element allows the generation of multiple concentric vortex beams with independent topological charges. The generalization of the phase mask for multiple concentric vortices is also shown. The design for a phase mask of two multiplexed vortices with different topological charges is developed. We experimentally show the transfer of angular momentum to the optically trapped microparticles by enabling orbiting dynamics around the optical axis independently within each vortex. The angular velocity of the confined particles versus the optical power in the focal region is also discussed for different combinations of topological charges.

physics.optics↗

Visualizing acoustical beats with a smartphones

In this work, a new Physics laboratory experiment on Acoustics beats is presented. We have designed a simple experimental setup to study superposition of sound waves of slightly different frequencies (acoustic beat). The microphone of a smartphone is used to capture the sound waves emitted by two equidistant speakers from the mobile which are at the same time connected to two AC generators. The smartphone is used as a measuring instrument. By means of a simple and free AndroidTM application, the sound level (in dB) as a function of time is measured and exported to a .csv format file. Applying common graphing analysis and a fitting procedure, the frequency of the beat is obtained. The beat frequencies as obtained from the smartphone data are compared with the difference of the frequencies set at the AC generator. A very good agreement is obtained being the percentage discrepancies within 1 %.

physics.ed-ph↗

Direct visualization of mechanical beats by means of an oscillating smartphone

The resonance phenomenon is widely known from Physics courses. Qualitatively speaking, it takes place in a driven oscillating system whenever the driven frequency approaches the natural frequency. It is when the amplitude of the oscillations become maximal. Very closely related to this phenomenon, there is another which is very surprising too. It takes place when the driven and natural frequencies of the system are slightly different and interfere constructively and destructively, forming the so called beats. The frequency of the beats is just the difference of the interfering waves frequencies. Beats are very noticeable in acoustic systems. We all have probably perceived them in the form of periodic ups and downs in the sound intensity volume. There are several works in this journal on visualizing the beats in acoustic systems. For instance, the microphone and the speaker of two mobile devices were used in previous work to analyze the acoustic beat produced by two signals of close frequencies. The formation of beats can also be visualized in mechanical systems, such as a mass-spring system5 or a double driven string. Hereafter, the mechanical beats in a smartphone-spring system are directly visualized in a simple way. The frequency of the beats is measured by means of the acceleration sensor of a smartphone which hangs from a spring attached to a motor driver.

physics.ed-ph↗