Projectile Motion Research Articles

Classification and determinants of passing difficulty in soccer: a multivariate approach

ABSTRACT Introduction Usually, the players’ or teams’ efficiency to perform passes is measured in terms of accuracy. The degree of difficulty of this action has been overlooked in the literature. Objectives The present study aimed to classify the degree of passing difficulty in soccer matches and to identify and to discuss the variables that most explain the passing difficulty using spatiotemporal data. Results The data used corresponds to 2,856 passes and 32 independent variables. The Fisher Discriminant Analysis presented 72.0% of the original grouped cases classified correctly. The passes analyzed were classified as low (56.5%), medium (22.6%), and high difficulty (20.9%), and we identified 16 variables that best explain the degree of passing difficulty related to the passing receiver, ball trajectory, pitch position and passing player. Conclusions The merit and ability of the player to perform passes with high difficulty should be valued and can be used to rank the best players and teams.In addition, the highlighted variables should be looked carefully by coaches when analyzing profiles, strengths and weaknesses of players and teams, and talent identification context. Practical Implications The values found for each variable can be used as a reference for planning training, such as small side games, and in future research.

Analysis of the structure and properties of triangular composite light-screen targets

Abstract With the development of light-screen targets for ballistic projectiles, not only must accuracy in the measurement of projectiles be assured but also the installation of the system and error compensation in the initial calibrations must be considered. We have designed a triangular composition light-screen target that is easy to install, derived expressions for the speed and direction of ballistic trajectories based on intersecting-CCD vertical targets, and conducted analyses of the points of impact and projectile speed. Results show that errors in the point of impact are affected by the coordinates of the target plane. Positional errors gradually increase with the distance from the origin. The horizontal angle error with the trajectory line does not exceed 0.3°, whereas the vertical angle error does not exceed 0.2°. Errors in the speed of the projectile remain relatively stable when the vertical coordinates are greater. Errors in speed and direction, as well as error fluctuations, are smaller on the x = 0 plane, making it the ideal region for error compensation in initial calibrations.

Serve Ball Trajectory Characteristics of Different Volleyballs and Their Causes

A floater serve in volleyball is a technique of serving a non-rotating or low-rotating ball, which is difficult to return because the flight path of the ball changes irregularly. On the other hand, the randomness of the trajectory makes it difficult for the ball to fall on the target. Players are required to serve taking into account the variability of the trajectory. In previous studies using wind tunnels, it was shown that aerodynamic characteristics such as drag force and lateral force applied to the ball vary depending on the type of ball and the orientation of the panel. Therefore, in order to control the flight trajectory, it is necessary to understand the aerodynamic characteristics of each ball. Since the velocity of the ball and the fluid force applied to the ball changes during flight, it is important to measure not only the fluid force at a steady state in the wind tunnel but also the actual flight distance of the ball. In this study, to provide valuable information for precise control of floater serves, we measured the drag force applied to the ball in a wind tunnel and the flight distance of the ball using an ejection machine, and clarified the effects of the type of ball and the panel face. In the drag force measurement, the drag force on three types of balls, V200W, MVA200, and FLISTATEC, was measured in the wind speed range of 4 m/s to 30 m/s. In the ejection measurement, the ball flight distances were measured while changing the orientation of the panel using an ejection machine. Basically, the FLISTATEC, MVA200, and V200W, in that order, were more likely to increase the distance and the variability, but it was shown that the drop point could be adjusted slightly by selecting the panel face. This result was also obtained when a human player actually served the ball, indicating the tactical importance of the player consciously controlling the direction of the panel. The tactical importance of the player’s conscious control of the direction of the panel was demonstrated. We also proposed receiver positions that would be effective based on the characteristics of each ball.

Interactive projectile motion STEM simulation and game, based on Scratch (S4A) and Arduino

A Science, Technology, Engineering and Mathematics (STEM) tool is proposed in this manuscript; which consists of an interactive, simple and low-cost computer based simulation and game, with the aim of easing the teaching/learning process regarding the physics concept of projectile motion. The novelty of this proposal relies on the use of a joystick shield used as the input device that changes the projectile shooting angle, the initial velocity and height in a simulation coded in S4A (Scratch for Arduino). The electronic interface is based on an Arduino UNO and a dual-axis joystick module. This educational resource is suitable to be implemented in graduate or undergraduate physics laboratories, classrooms or even at home.

Research on small caliber weapons firing ranges security enhancement considering the projectile-obstacle impact

Weapons systems are used to gain a tactical, strategic, material or mental advantage over an adversary or enemy target. The modern weapons systems are designed to be technologically complex but practical for operator usage. The firing phenomenon consists of a multitude of mechanical and thermodynamic processes with the result being the movement of the projectile towards a chosen target. The projectile movement from the weapon to the point of impact defines its trajectory.Firing ranges are locations where military personnel is operating certain weapons systems in order to achieve specific results and certain levels of readiness. Due to increasing urbanisation of the areas adjacent to firing ranges, monitoring the projectile trajectory becomes mandatory in order to be able to provide a secure climate for both military personnel and civilians.It is the purpose of the author to provide the numerical simulation tool (a MATLAB application) which is useful for tracking the projectile trajectory from the muzzle of the weapon to the impacted obstacle. By computing the useful information obtained with the internal and external ballistics, the theoretical trajectory of a projectile can be calculated. In order to get the most accurate values, preliminary knowledge is needed. So by using appropriate tools and software, a projectile’s trajectory can be calculated if the correct values are provided (mass, diameter, initial angle, initial speed). The tool created has different weapons-ammunition specifications and initial conditions parameters loaded that can be combined with the existing drag laws known in ballistics (Siacci law, 1930 law or 1943 law) to describe the projectile movement in atmosphere. As obstacles are defined, similar to the ones existing in a firing range, the tool can assess where the impact occurred and is able to display necessary values (impact points coordinates, velocities, impact angles, etc) while also creating 3D and 2D visualisations on the integrated graphic area. This way, the tool can be used to create impact assessments for specific weapons systems and decisions can be made to enhance the security of the firing range and the firing safety.Three different firing range configurations are considered for comparison when using certain small caliber weapons used by NATO countries.

Smart Table Tennis Racket with Tunable Stiffness for Diverse Play Styles and Unconventional Technique Training (Adv. Mater. Technol. 10/2021)

Smart Table Tennis Racket In article number 2100535, Mengying Zhang, Jinbo Wu, and coworkers invent a smart table tennis racket with tunable stiffness based on electrorheological elastomers. The racket face is a multilayer structure of rubber, soft electrode, anisotropic electrorheological elastomer and copper electrode. By applying an electric field, the smart racket successfully changed the trajectory of balls, reduced ejection angle and increased ejection velocity to adapt to diverse play styles and improve unconventional play technique.

Misconceptions in Projectile Motion and Conceptual Changes via Geogebra Applications

The purpose of this work is to examine the issue of pre-service science teachers’ (PSST) Geogebra applications on misconceptions about projectile motion (PM) and the permanence of learning concepts. In this study, quantitative research method was used as scientific research method, and semi-experimental design with pre-test, post-test control group was used as a pattern. The accessible population of this study is PSST who study in a university located in Kayseri, Turkey in the 2019-2020 academic year. Sample of the study included 36 freshman PSST, studying at the university level in Kayseri. 18 of the participants are experimental-group (EG) and 18 of them are control-group (CG). Both groups learned the subject of projectile motion (PM) together in the classroom. In addition to the traditional teaching method, the EG participated eight-week in the Geogebra course based on the conceptual change model and prepared physics simulations with Geogebra. “Conceptual Questions on Projectile Motion” was used as a data collection tool and the data were analyzed by means of statistics (t-test) based on the difference between averages. The results revealed that both the post-test’s and permanence test’s mean scores of the EG PSST were significantly higher than the mean score of the CG PSST (post-test: t=2.525; p< .05) (permanence test: t=5.466; p< .05). Furthermore, in this study, many misconceptions about the PM were identified.

The pulsed rocket on a mass–momentum diagram

We propose a new method to investigate the motion of a pulsed rocket in Newtonian mechanics using a mass–momentum diagram. We can draw the state of the rocket motion step-by-step on the diagram without any calculations. We also obtain the equation of the trajectory of the state on the diagram and deduce the relation between the final velocity and mass of the rocket, which coincides with the ordinary prescription of the textbooks.

Trajectories of a ball moving inside a spherical cavity using first integrals of the governing nonlinear system

Analytical study of ball vibration absorber behavior is presented in the paper. The dynamics of trajectories of a heavy ball moving without slipping inside a spherical cavity are analyzed. Following our previous work, where a similar system was investigated through various numerical simulations, research of the dynamic properties of a sphere moving in a spherical cavity was carried out by methods of analytical dynamics. The strategy of analytical investigation enabled definition of a set of special and limit cases which designate individual domains of regular trajectories. In order to avoid any mutual interaction between the domains along a particular trajectory movement, energy dissipation at the contact of the ball and the cavity has been ignored, as has any kinematic excitation due to cavity movement. A governing system was derived using the Lagrangian formalism and complemented by appropriate non-holonomic constraints of the Pfaff type. The three first integrals are defined, enabling the evaluation of trajectory types with respect to system parameters, the initial amount of total energy, the angular momentum of the ball and its initial spin velocity. The neighborhoods of the limit trajectories and their dynamic stability are assessed. Limit and transition special cases are investigated along with their individual elements. The analytical means of investigation enabled the performance of broad parametric studies. Good agreement was found when comparing the results achieved by the analytical procedures in this paper with those obtained by means of numerical simulations, as they followed from the Lagrangian approach and the Appell–Gibbs function presented in previous papers.

Hand-related action words impair action anticipation in expert table tennis players: Behavioral and neural evidence.

Athletes extract kinematic information to anticipate action outcomes. Here, we examined the influence of linguistic information (experiment 1, 2) and its underlying neural correlates (experiment 2) on anticipatory judgment. Table tennis experts and novices remembered a hand- or leg-related verb or a spatial location while predicting the trajectory of a ball in a video occluded at the moment of the serve. Experiment 1 showed that predictions by experts were more accurate than novices, but experts' accuracy significantly decreased when hand-related words versus spatial locations were memorized. For nonoccluded videos with ball trajectories congruent or incongruent with server actions in experiment 2, remembering hand-related verbs shared cognitive resources with action anticipation only in experts, with heightened processing load (increased P3 amplitude) and more efficient conflict monitoring (decreased N2 amplitude) versus leg-related verbs. Thus, action anticipation required updating of motor representations facilitated by motor expertize but was also affected by effector-specific semantic representations of actions, suggesting a link from language to motor systems.

Laboratory measurements of size distribution of electrostatically lofted dust

Electrostatic dust lofting has been suggested to explain a number of unresolved phenomena on airless planetary bodies such as the lunar horizon glow, the dust ponds on asteroid Eros, and the radial ‘spokes’ in Saturn’s rings. In this paper we report laboratory measurements of the size distribution of lofted dust particles in the range of 1 to 40 μm in diameter. It is shown that the population of lofted dust increases with a decrease in dust size (i.e., smaller sized dust is easier to be lofted), which is in agreement with the theoretical expectation derived from the patched charge model (Wang et al., 2016a). Additionally, initial launch velocities are derived from transport distances of lofted particles following ballistic trajectories. It is shown that the initial velocity of lofted particles is inversely proportional to their size, in agreement with an earlier work that used a different measurement method (Carroll et al., 2020).

Exploring Students’ Misconception in the Frame of Graphic and Figural Representation on Projectile Motion Regarding to the COVID-19 Constraints

Remote learning has reformed the normal tradition of physics instruction in the existence of COVID-19 pandemic. The previous documentation of student’s misconception is mostly discovered in the normal condition of physics instruction. Regarding to the pandemic outbreak is necessary since distance learning routines have absolutely influence the physics education outcomes all over the world. To explore the issues, this quantitative study has descriptively identified students' misconception on projectile motion in the frame of graphic and figural representations. The six items of Busyairi and Zuhdi’s three tier test were administered to the 76 students in a Javanese public high school, Indonesia. Overall, the Arslan, Cigdemolu, & Moseley’s categorical framework classified that the whole participants still congregate in the misconception’s groups on projectile motion. The lack of students’ representation on projectile motion might be magnified by the pandemic restrictions in providing appropriate visualization on projectile concept. Finally, the author suggested that the alternative of online learning during the outbreak have not yet been effectively engaged to promote the physics representation on projectile motion.

Simulation and Analysis of Muzzle Arc of Electromagnetic Rail Launch

Arc ignition technology is one of the most feasible strategies for releasing the residual energy of electromagnetic rail launch (EMRL). The muzzle arc characteristic must be considered in the design of arc ignition devices, because it is a main factor affecting the intermediate ballistic trajectory. Based on the theory of magnetohydrodynamics (MHDs), this work has made numerical simulation of muzzle arc and analyzed the temperature field, electromagnetic (EM) field, and flow field of the muzzle arc at different stages. The results show that the temperature is the highest, the EM field is the most intensive, and the flow is the strongest at the initial stage of the muzzle arc. The optimization of arc ignition device is pointed out to be reducing the current transfer time to improve the temperature, EM, and flow environments of the launcher, projectile, and guidance device.

Shooting-projection method for a small object moving under the influence of a force

We consider a small object in 3D moving under the influence of a force that may depend explicitly on time, on the position of the object, and on its velocity. The equations of motion of classical mechanics are assumed to hold. If the position of the object is specified at some initial and some final time, obtaining the trajectory of the object requires the solution of a two-point boundary value problem. To solve the problem various numerical technics can be applied. This paper extends the recently proposed shooting-projection method to 3D. We introduce a Lagrangian from which, applying the principle of least action, the projection trajectory is derived. Analysis of the action reveals the meaning of the projection trajectory. Using the shooting-projection method, the considered two-point boundary value problem is solved for the case of a projectile motion in the presence of air resistance and wind.

Analisis Bifurkasi Persamaan Longitudinal pada Gerak Roket Tiga Dimensi Tipe RKX-Lapan

This article discusses about longitudinal equation for the three dimensional rocket motion of RKX-Lapan. The RKX-Lapan’s rocket is guided rocket which was designed using two phases, boosting and sustaining. The rocket has six degrees of freedom movement. The freedom movements consists of three translational motions and three rotational motions which causess unstable rocket movement. Therefore, stable rocket motion system is needed. The rocket motion system is three dimensional of nonlinear equation, thus linearization process of rocket motion equation is requaired. One of this linearization process is longitudinal motion which consists of two translational motions and one rotational motion. The equation of longitudinal motion has stabilization system analysist on sustaining phase. Bifurcation analysis of longitudinal equation for the three dimensional rocket motion of RKX-Lapan has been created in this article. It determined equilibria and its equation stability character. Furthermore, bifurcation analysist on equilibria and numerical simulation have been done to find out that bifurcation value indicated a topologically nonequivalent.

The Effect of Judgement Bias on Cue Utilization for Shot Prediction in Basketball Athletes.

Background: Concerning the judgments bias and cue utilization in basketball athletes, previous shot anticipation tasks were hard to examine in regards to whether the experts’ judgement bias relies more on the cue of the player’s body or the ball trajectory. Methods: Four types of body–ball cues shots were employed: IN–IN, IN–OUT, OUT–IN, and OUT–OUT. Four temporal stages (i.e., shooting, rising, high point, and falling) were divided during a shot. Forty-two participants predicted the fate of the ball after watching the shot videos. Results: The results suggested that for the shooting, rising, and high point phase, compared to the non-athletes, the experts provided superior predictions for IN–IN condition and OUT–IN condition but fewer accurate predictions for IN–OUT condition and OUT–OUT condition. Moreover, a higher bias toward predicting the shots as “in” for the athletes than the non-athletes under early temporal conditions was confirmed. Conclusions: These findings strengthen the idea that the IN cues from both body information and ball trajectory could elicit the experts’ judgement bias for made shots and then influence their response, thus rendered two distinct (e.g., impeding and facilitating) effects for the incongruent body–ball cues, respectively.

AMERICAN ANTI-MISSLE SHIELD, EASTERN EUROPEAN ASSET TO DISCOURAGE BALLISTIC ATTACKS

Abstract: Air-missile defense is a mission of anti-aircraft missile troops known in the field as anti-missile shield. It describes an anti-ballistic area intended for research, discovery, interception and combat of surface-to-air or air-to-air missiles with ballistic trajectory. The existence of the anti-missile shield implies the creation of a security zone of allied states, institutional structures and population that can ensure their functionality and existence, deployed on an alignment (territories of several states), in order to maintain a state of normalcy and security. This defense system must include the threatened states, members of the politico-military alliance, regardless of their economic and military power. The security environment also concerns both the population of those countries and the objectives of great political, economic, strategic, critical and military infrastructure importance.

Smart Table Tennis Racket with Tunable Stiffness for Diverse Play Styles and Unconventional Technique Training

AbstractSmart technologies bring innovation to the life and sports arena. To adapt to diverse play styles and improve unconventional technique of table tennis players, a smart table tennis racket with tunable stiffness based on anisotropic electrorheological elastomers (EREs) is developed. The EREs are prepared in the designed mold under the electric field to form an anisotropic structure that consisted of electrorheological particles and facilitated the generation of interparticle saturation surface polarization and the local electric field. Therefore, the electrorheological property of anisotropic EREs is significantly promoted, attaining a relative electrorheological effect of 17 160% in shear mode, and the incremental shear storage and compression modulus of 5.2 and 6.4 MPa. By applying an electric field, the smart racket successfully changes the trajectory of balls, reduced ejection angle by 11% and increased ejection velocity by 2%.

Aerodynamic Differences between New and Used Soccer Balls

The surface structure of soccer balls, such as the number and shapes of the ball panels, has recently changed, and research on the aerodynamics and flight trajectories of new soccer balls is actively proceeding. However, these studies are focused on new soccer balls, whereas the used soccer balls were never studied. In this study, the aerodynamic characteristics of soccer balls kicked 1000 times by a robot were investigated through wind tunnel tests. The results were compared with those obtained using new soccer balls. Regarding the aerodynamic characteristics of the soccer balls, it was found that the critical Reynold number, Recrit, changes with usage. This is related to the transition from laminar to turbulent flow of airflow around the ball. The comparison of the drag coefficients of the balls at Recrit showed that the drag coefficients of the new and used Telstar18 balls were 0.15 (Re = 2.5 × 105) and 0.14 (Re = 2.2 × 105), respectively; those of the new and used Merlin were 0.13 (Re = 2.8 × 105) and 0.13 (Re = 2.2 × 105), respectively; and finally, those of the new and used Derbystar were 0.14 (Re = 2.1 × 105) and 0.14 (Re = 2.1 × 105), respectively. The surface conditions of a soccer ball, such as the surface roughness and surface damages, are essential factors to determine the aerodynamics of the soccer balls.

Dust Outburst Dynamics and Hazard Assessment for Close Spacecraft–Comet Encounters

Abstract Using the gas drag by sublimating cometary surface ices for the acceleration of dust particles and deceleration by the gravity field of the nucleus combined with basic laws of mechanics, the sizes, velocities, and number densities of escaping particles are calculated and evaluated with respect to the hazard assessment of comet–spacecraft flybys and encounters. We find good agreement between our analytical method and the more elaborate and precise DSMC calculations, but, being simpler, our method can more easily be used to explore a wide range of cometary conditions and can be more easily scaled to specific comets with different nucleus sizes, masses, and gravity potentials and various gas and dust production rates. Our analytical method is applied to outbursts expanding into a cone of ∼60°, where the gas density falls off with height from the surface rather than radial distance from the center of a uniformly outgassing nucleus. In this scenario, larger dust particles can be ejected and attain ballistic trajectories, go into orbit, or escape from the nucleus, thus being potentially more hazardous to a spacecraft. Sample calculations are carried out for potential dust outbursts for the highly active Centaur/Comet 29P/Schwassmann-Wachmann 1 for various assumed active areas and dust particle size distributions. Particle velocity ranges for ballistic trajectories, orbiting particles, and particles escaping into the coma are presented. These calculations are used to estimate the coma particle number densities during outbursts to get an assessment of the hazards and required mitigation for a flyby or orbiting space mission.