César Mora

Third quantization of Brans–Dicke cosmology

Abstract We study the third quantization of a Brans–Dicke toy model, we calculate the number density of the universes created from nothing and found that it has a Planckian form. Also, we calculated the uncertainty relation for this model by means of functional Schrodinger equation and we found that fluctuations of the third-quantized universe field tends to a finite limit in the course of cosmic expansion.

The magic blower: a discrepant experiment in the learning of the Bernoulli's Law of hydrodynamic pressure

The main purpose of this article is to present a discrepant experiment, its physical modeling as well as its pedagogical benefits of the assembly to learn the Bernoullis Law of hydrodynamic pressure. The impact of the results is presented on a population of students and the interactive engagement is measured starting from a process of dissonance to a process of consonance. The prototype has been implemented as a project in order that the students population makes time by their own during four weeks. The evolution of the learning process is specified with the Hakes average normalized gain and the Baos concentration factor. The experience has turned out to be quite fruitful from a pedagogical standpoint represented by the Hakes gain values above 0.5.

Experimentos virtuales sobre una mosca vagabunda: más allá de la solución de Neumann

We extend the traditional problem of calculating the distance of travel of a fly that is moving with constant speed along a straight path between two trains that are approaching one another. We found two analytical solutions for the traditional problem and we propose a generalization to the accelerated motion of the trains through a simulation. With this problem the teachers can teach some topics of basic physics as the relations between mathematics and physics, the graphical analysis and various situations on kinematics in one dimension. We show an analogy between the motion of the fly and a ultrasonic wave pulse in a sensor of velocity, which indicates the pedagogical power of this problem.

Enseñanza de la Electrostática por Medio de la Construcción de Prototipos de Bajo Costo y el Aprendizaje Basado en Proyectos

This work presents the results of a teaching strategy based on Projects Based Learning which was applied in a course of Electricity and Magnetism for engineering students of the Colombian School of Engineering in the first semester of 2015. The students were required to construct low cost prototypes that let them to use concepts of physical modeling and error theory. The methodology employed stimulates and increases the learning of electrostatics and of other abilities such as graphical, oral and written expression. This paper describes the method used and the instruments that were used for the data collection process. Analyses show a gain of (0.78 ± 0.03) and (0.65 ± 0.04) for the evaluation of the projects and (0.47 ± 0.04) for an electrostatic conceptual test. The paper presents and discusses the strengths and difficulties of the strategy employed.

Diseño y Construcción de una Máquina de Wimshurst para La Enseñanza de la Electrostática

En este trabajo se presenta el diseno y construccion de un prototipo de una Maquina de Wimshurst, explicando cuales son las partes importantes que conforman la maquina y el principio fisico de su funcionamiento. El prototipo fue empleado para la ensenanza de la Electrostatica en cursos de laboratorio de Electricidad y Magnetismo en la Escuela Colombiana de Ingenieria. El prototipo se uso con dos enfoques. El primer enfoque se direcciona a que los estudiantes realicen practicas demostrativas a nivel de descargas electricas controladas y pendulo electrostatico. El segundo enfoque se orienta a que los estudiantes experimenten y obtengan resultados cuantitativos para un laboratorio a nivel de Campo y Potencial Electrico. Los resultados muestran una ganancia de 0.52 ± 0.08 y corresponde a un rango de ganancia medio (entre 0.3 y 0.7). Se presenta la secuencia didactica que siguen los estudiantes cuando realizan los laboratorios con el prototipo construido. En este trabajo tambien se describe el metodo usado y los instrumentos que se emplearon para el proceso de obtencion de datos. Asi mismo el trabajo presenta y discute las fortalezas de la estrategia empleada.

Estimación del tiempo de iluminación solar sobre la tierra mediante un modelo analítico: un escenario fértil para enseñar física

We proposed an analytical model for the calculus of illumination time of the Earth for any time of year and any latitude. This model assumes the obliquity of the ecliptic as constant, the light beams as parallels, the Earth as spherical, the movement of translation of Earth as uniform circular. Also, this model showed a context of the astronomy whereby the teachers can teach the basic physics. It was built through a relationship between the movement of translation and of rotation of the wave front light, then we found the illumination zone on the Earth, and the illumination time is estimated in a particular latitude with the uniform circular movement of Earth. The present model was confronted with the numerical results of the Geoscience Australia Agency and it is found a maximum percent error of 1,6%, which was due primarily to the difference between the circular trajectory, in this model, and the real elliptical trajectory. Without the use of spherical trigonometry, it was obtained an analytical model that estimates very close the solar illumination time at any time of the year and at any latitude on Earth. This model provides an authentic context for studying basic aspects of physics.

Experimentos de mecánica con temporizador de bajo costo

We have made a mechanical system that consists of a base and a vertical axis that supports a rail. In the ends of the rail two photogates have been prepared. The photogates have been designed and constructed to measure time intervals of rigid solids that move on the rail and that happen for the photogates. The prototype is of low cost and is used for practices of laboratory concerning with kinematics and dynamics of translation, and dynamics of the rigid solid in mechanics courses.

CLASSICAL AND QUANTUM COSMOLOGY WITH AND WITHOUT SELF-INTERACTING SCALAR FIELD IN BERGMANN-WAGONER THEORY

Classical and quantum cosmologies are considered in the context of generalized scalar-tensor theories of gravitation of Bergmann-Wagonner (BW) for Isotropic, and the Bianchi types I and II cosmologies with and without self interactions of the scalar field. The coupling function ω(φ) is kept arbitrary and the self interacting potential is chosen to obtain exact solutions. Quantum wormholes and classical non-singular solutions are given.