arXiv subjects

Martin Monteiro

Publications and source records attributed to Martin Monteiro.

At least 19 recordsLinked to original sources

arXiv2024

Cooling of an objetct by forced convection

We present an experiment on forced convection where a previously heated object is cooled under the effect of a controlled stream of air. We consider a square copper plate in which temperature variations can be considered negligible and we measure the cooling rate as a function of the average velocity of the air stream. We use a thermal camera to measure the temperature field and the cooling curves as a function of time for different conditions. An empirical relation between the characteristic cooling time and the mean velocity of the air stream is reported. The results obtained are discussed in the framework of simple dimensional models and their limits of validity.

physics.ed-ph↗

arXiv2022

A home-lab to study uncertainties using smartphone sensors and determine the optimal number of measurements

We present a home-lab experimental activity, successfully proposed to our students during covid19 pandemic, based on \textit{state-of-the-art} technologies to teach error analysis and uncertainties to science and engineering students. In the last decade the appearance of smartphones considerably affected our daily life. Thanks to their built-in sensors, this revolution has impacted in many areas and, in particular, the educational field. Here we show how to use smartphone sensors to teach fundamental concepts for science students such as any measurement is useless unless a confidence interval is specified or how to determine if a result agrees with a model, or to discern a new phenomenon from others already known. We explain how to obtain and analyse experimental fluctuations and discuss in relation with the Gaussian distribution. In another application we show how to determine the optimal number of measurements as a function of the standard error and the digital resolution of a given sensor.

physics.ed-ph↗

arXiv2022

A home-lab experiment: resonance and sound speed using telescopic vacuum cleaner pipes

We propose a home laboratory in which a telescopic vacuum cleaner pipe and a smartphone are used to investigate sound speed and acoustic resonance. When the pipe is hit or the hands clapped near one end the sound produced is registered by a smartphone. By means of an appropriate application the resonant frequency is obtained. Varying the pipe's length and registering the corresponding resonant frequency allows to obtain the sound speed. This home-lab, first proposed during covid19 pandemic, has been incorporated as a home challenge to experiment with acoustic resonance in new normal times.

physics.ed-ph↗

arXiv2022

The sensors of mobile devices: a innovative tool in the teaching of physical sciences

We show how builtin sensors in mobile devices can be used as portable laboratories at the service of teaching experimental sciences, especially physics, in the last years of high school and first years of university. We describe experiments that previously required expensive apparatus or were not feasible in teaching laboratories. Finally, we discuss some perspectives about the use of sensors in the physics teaching.

physics.ed-ph↗

arXiv2022

Mobile Devices and Sensors for Physics Teaching

This Resource Letter provides a guide to the literature on teaching experimental physics using sensors in tablets, smartphones, and some specialized devices. After a general discussion of the hardware (sensors) and the software (apps), we present resources for experiments using mobile-device sensors in many areas of physics education: mechanics, oscillations and waves, optics, electromagnetism, matter, modern physics, and astronomy.

physics.ed-ph↗

arXiv2022

Differences in the attitudes and beliefs about science of students in the physics-mathematics and life sciences areas and their impact on teaching

For this study, we compared the attitudes and beliefs about science of physical science (physics and mathematics) and life science (biochemistry and biology) students at the beginning of their university degrees using the CLASS (Colorado Learning Attitudes about Science Survey) tool. It is worth noting that both groups of students received similar physics courses during their high-school education. Through a detailed analysis of the different categories of the test, we examined the differences in performance in each of the areas that make up the questionnaire. Among other aspects, we found that a considerable percentage of life science students (higher than that of physical science students) adopted a novice type of behavior in problem solving. Finally, we discussed the possible causes of the differences found and their implications for teaching.

physics.ed-ph↗

arXiv2021

How far away is infinity? An electromagnetic exercise to develop intuition regarding models

The estimation of the electric field in simple situations provides an opportunity to develop intuition about the models used in physics. We propose an activity aimed at university students of General Physics where the electric field of a finite line of charge is compared, analytically or numerically, with the fields of an infinite line and of a point charge. Contrary to intuition, it is not necessary to get very close for the line charge to be considered infinite, nor to move very far away for the finite line field to resemble that of a point charge. We conducted this activity with a group of students and found that many of them have not yet developed an adequate intuition about the approximations used in electromagnetism.

physics.ed-ph↗

arXiv2020

Bernoulli's muddle: a research on students' misconceptions in fluid dynamics

Bernoulli's equation, which relates the pressure of an ideal fluid in motion with its velocity and height under certain conditions, is a central topic in General Physics courses for Science and Engineering students. This equation, frequently used both textbooks as in science outreach activities or museums, is often extrapolated to explain situations in which it is no longer valid. A common example is to assume that, in any situation, higher speed means lower pressure, a conclusion that is only acceptable under certain conditions. In this paper we report the results of an investigation with university students on some misconceptions present in fluid dynamics. We found that after completing the General Physics courses, many students have not developed a correct model about the interaction of a fluid element with its environment and extrapolate the idea that higher speed implies lower pressure in situations where it is no longer valid. We also show that an approach to fluid dynamics based on Newton's laws is more natural to address these misconceptions.

physics.ed-ph↗

arXiv2020

Using mobile-device sensors to teach students error analysis

Science students must deal with the errors inherent to all physical measurements and be conscious of the need to expressvthem as a best estimate and a range of uncertainty. Errors are routinely classified as statistical or systematic. Although statistical errors are usually dealt with in the first years of science studies, the typical approaches are based on manually performing repetitive observations. Our work proposes a set of laboratory experiments to teach error and uncertainties based on data recorded with the sensors available in many mobile devices. The main aspects addressed are the physical meaning of the mean value and standard deviation, and the interpretation of histograms and distributions. The normality of the fluctuations is analyzed qualitatively comparing histograms with normal curves and quantitatively comparing the number of observations in intervals to the number expected according to a normal distribution and also performing a Chi-squared test. We show that the distribution usually follows a normal distribution, however, when the sensor is placed on top of a loudspeaker playing a pure tone significant differences with a normal distribution are observed. As applications to every day situations we discuss the intensity of the fluctuations in different situations, such as placing the device on a table or holding it with the hands in different ways. Other activities are focused on the smoothness of a road quantified in terms of the fluctuations registered by the accelerometer. The present proposal contributes to gaining a deep insight into modern technologies and statistical errors and, finally, motivating and encouraging engineering and science students.

physics.ed-ph↗

arXiv2020

Inconsistencies and errors in traditional approaches to energy in our introductory courses

We present a critical analysis of the classical approaches to energy subjects, based on the work-energy theorem and the conservation of mechanical energy proposed in the courses of the first years of tertiary education. We show how these approaches present a series of inconsistencies and errors that are a source of conceptual difficulties among students. We then analyze a modern treatment of mechanical courses based on the results of research in physics education over the last 40 years. We place special emphasis on the principle of conservation of energy as one of the fundamental principles of nature, prioritizing the concepts of system, surrounding, and energy transfer and transformation.

physics.ed-ph↗

arXiv2020

Magnetic fields produced by electric railways

We propose a simple experiment to explore magnetic fields created by electric railways and compare them with a simple model and parameters estimated using easily available information. A pedestrian walking on an overpass above train tracks registers the components of the magnetic field with the built-in magnetometer of a smartphone. The experimental results are successfully compared with a model of the magnetic field of the transmission lines and the local Earth's magnetic field. This experiment, suitable for a field trip, involves several abilities, such as modeling the magnetic field of power lines, looking up reliable information and estimating non-easily accessible quantities.

physics.ed-ph↗

arXiv2020

A student experiment on error analysis and uncertainties based on mobile--device sensors

Science students must deal with the errors inherent to all physical measurements and be conscious of the necessity to express their as a best estimate and a range of uncertainty. Errors are routinely classified as statistical or systematic. Although statistical errors are usually dealt with in the first years of science studies, the typical approaches are based on performing manually repetitive observations. Here, based on data recorded with the sensors present in many mobile devices a set of laboratory experiments to teach error and uncertainties is proposed. The main aspects addressed are the physical meaning of the mean value and standard deviation, and the interpretation of histograms and distributions. Other activities focus on the intensity of the fluctuations in different situations, such as placing the device on a table or held in the hand in different ways and the number of measurements in an interval centered on the mean value as a function of the width expressed in terms of the standard deviation. As applications to every day situations we discuss the smoothness of a road or the different positions to take photographs both of them quantified in terms of the fluctuations registered by the accelerometer. This kind of experiments contributes to gaining a deep insight into modern technologies and statistical errors and, finally, to motivate and encourage engineering and science students.

physics.ed-ph↗

arXiv2020

Normal coordinates in a system of coupled oscillators and influence of the masses of the springs

Experimental analysis of the motion in a system of two coupled oscillators with arbitrary initial conditions was performed and the normal coordinates were obtained directly. The system consisted of two gliders moving on an air track, joined together by a spring and joined by two other springs to the fixed ends. From the positions of the center of mass and the relative distance, acquired by analysis of the digital video of the experiment, normal coordinates were obtained, and by a non linear fit the normal frequencies were also obtained. It is shown that although the masses of the springs are relatively small compared to that of the gliders, it is necessary to take them into consideration to improve the agreement with the experimental results. This experimental-theoretical proposal is targeted to an undergraduate laboratory.

physics.ed-ph↗

arXiv2020

Using smartphones as hydrophones: two experiments in underwater acoustics

During the last years, it has become increasingly clear that smartphones are valuable tools to be used almost everywhere. Until recently, a place that still resisted smartphone onslaught was the aquatic media. However, nowadays, many modern smartphones are waterproof and the performance of their microphones results sufficiently adequate to employ them as hydrophones. This capability gives rise to several interesting applications. Here, we describe two experiments in underwater acoustics which require two smartphones -- at least one should be waterproof. The first experiment consists in a simple time-of-flight measurement of the sound speed in water and the comparison with the corresponding value in air. The second experiment deals with the acoustic location -- or ranging -- of a distant object by comparing the time it takes for the sound to reach the object travelling in two different media (air and water in this case) with known sound speed.

physics.ed-ph↗

arXiv2019

Smartphone sensors and video analysis: two allies in the Physics laboratory battle field

Recently, two technologies: video analysis and mobile device sensors have considerable impacted Physics teaching. However, in general, these techniques are usually used independently. Here, we focus on a less-explored feature: the possibility of using supplementary video analysis and smartphone (or other mobile devices) sensors. First, we review some experiments reported in the literature using both tools. Next, we present an experiment specially suited to compare both resources and discuss in detail some typical results. We found that, as a rule, video analysis provides distances or angular variables, while sensors supplies velocity or acceleration (either linear or angular). The numerical differentiation of higher derivatives, i.e. acceleration, usually implies noisier results while the opposite process (the numerical integration of a temporal evolution) gives rise to the accumulation of errors. In a classroom situation, the comparison between these two techniques offers an opportunity to discuss not only concepts related to the specific experiment but also with the experimental and numerical aspects including their pros and cons.

physics.ed-ph↗

arXiv2019

Experimental analysis of a physical pendulum with variable suspension point

A physical pendulum with variable point of suspension (and, as an outcome, variable inertia moment) is experimentally analysed. In particular, the period of the small oscillations as a function of position of the suspension point is measured using three different methods: a smartphone used both as an independent tool or as a data-logger and commercial photo-gate. The experimental results are successfully compared with theoretical calculations based on the addition of inertia moments and the Steiner theorem.

physics.ed-ph↗

arXiv2019

Dynamics of a yoyo using a smartphone gyroscope sensor

The dynamics of a traditional toy, the yoyo, is investigated theoretically and experimentally using smartphone' sensors. In particular, using the gyroscope the angular velocity is measured. The experimental results are complemented thanks to a digital video analysis. The concordance between theoretical and experimental results is discussed. As the yoyo is a ubiquitous, simple and traditional toy this simple proposal could encourage students to experiment with everyday objects and modern technologies.

physics.ed-ph↗

arXiv2019

Sensors based on micromechanical devices: mobile labs at the service of experimental science teaching

In this paper we discuss the use of sensors incorporated in mobile devices as possible mobile laboratories at the service of teaching experimental sciences. Mobile devices, smartphones, tablets, laptops, microbit cards, are a resource for making measurements of the physical world, since they have a set of built-in sensors that allow to measure position, linear speed, angular speed, acceleration, pressure, sound, color, magnetic field, proximity or luminosity, among others. Also, these devices have greatly improved the performance of their video cameras, allowing to easily shoot at high speed and high resolution. Given its portability it is possible to work in the laboratory itself or in other areas such as a gym, a park or your own home, transcending the traditional scope of the laboratory. In general, the measurements obtained can be analyzed in the device itself or uploaded to the cloud to be analyzed la

physics.ed-ph↗