Motion of a circular cylinder on a smooth surface

2009 ◽  
Vol 87 (6) ◽  
pp. 607-614 ◽  
Author(s):  
Mark R.A. Shegelski ◽  
Ian Kellett ◽  
Hal Friesen ◽  
Crystal Lind
Keyword(s):  
Circular Cylinder ◽  
Undergraduate Students ◽  
Smooth Surface ◽  
Equations Of Motion ◽  
Static Friction ◽  
Circular Motion ◽  
Pedagogical Treatment ◽  
Newton’S Laws ◽  
Made In

We present a pedagogical treatment of a circular cylinder moving over a smooth surface with one point of the cylinder making contact with the surface. We derive the equations of motion using Newton’s laws. The simplicity of this approach makes the results easily within reach of undergraduate students. A careful derivation of the equations is presented first, and then we show how easily one could make an error. We illustrate how instructors could use this calculation to teach students how to detect errors and critically examine assumptions, including those that seem beyond question. Circular motion with no slipping is examined and we demonstrate the extent of possible motions for static friction. Some calculations are listed that instructors can assign to students to teach the points made in this paper.

The response of a turbulent boundary layer to lateral divergence

1979 ◽  
Vol 94 (2) ◽  
pp. 243-268 ◽  
Author(s):  
A. J. Smits ◽  
J. A. Eaton ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Structural Parameters ◽  
Axial Flow ◽  
Turbulence Structure ◽  
Two Dimensional ◽  
Transition Section ◽  
Two Dimensional Flow ◽  
Made In

Measurements have been made in the flow over an axisymmetric cylinder-flare body, in which the boundary layer developed in axial flow over a circular cylinder before diverging over a conical flare. The lateral divergence, and the concave curvature in the transition section between the cylinder and the flare, both tend to destabilize the turbulence. Well downstream of the transition section, the changes in turbulence structure are still significant and can be attributed to lateral divergence alone. The results confirm that lateral divergence alters the structural parameters in much the same way as longitudinal curvature, and can be allowed for by similar empirical formulae. The interaction between curvature and divergence effects in the transition section leads to qualitative differences between the behaviour of the present flow, in which the turbulence intensity is increased everywhere, and the results of Smits, Young & Bradshaw (1979) for a two-dimensional flow with the same curvature but no divergence, in which an unexpected collapse of the turbulence occurred downstream of the curved region.

scholarly journals Is Grit the Key Element to Improve the Life Attitude? A Study with Military Students from Argentina

2019 ◽  
Vol 2 (3) ◽  
pp. 30
Author(s):  
María Cecilia Barni ◽  
Florencia Teresita Daura
Keyword(s):  
Undergraduate Students ◽  
Ad Hoc ◽  
Personal Relationships ◽  
Military Students ◽  
National Defense ◽  
Attitude Test ◽  
National Defense University ◽  
First Results ◽  
Probabilistic Sample ◽  
Made In

The main goal of the study is to analyze the link between Grit and Life Attitude, and its relation with the permanence and academic performance of students from the National Defense University. This paper is mainly focused in the link between the first two constructs. Grit is defined as the passion and constancy to achieving goals, to resisting with effort and interest towards the challenges and difficulties, which is a leader’s attribute (Duckworth, Peterson, Matthews y Kelly, 2007). Life Attitude based on the existential belief that life has a purpose, that persons draw meaning from a variety of sources: recreational and creative activities, personal relationships, achievements (Reker - Woo, 2011). A non-probabilistic sample was formed, for convenience, of 162 students; a sociodemographic questionnaire designed ad hoc; the Scale of Determination (Grit Scale) (Duckworth et al., 2007), which is in the process of validation (Tortul and Daura, in evaluation) and the Life Attitude Test (LAP-R (VE-AA)) in the Spanish adaptation of Barni (2017) were administered. Statistical analysis were made from the collected data, in order to corroborate if there were differences in the variables. The first results showed differences according to career and sociodemographic variables; the undergraduate students obtained higher scores in the positive dimensions of the LAP-R than in other researches made in the same geographical context. The work evidences data of interest in the training of defense professionals, for the decision making in the educational style necessary for an integral formation as a lifelong process.

scholarly journals Education for sustainable development – from students’ and geography teachers’ knowledge to educational activities

2019 ◽  
Vol 23 (1) ◽  
pp. 47-52
Author(s):  
Joanna Angiel ◽  
Wojciech Pokojski
Keyword(s):  
Sustainable Development ◽  
Undergraduate Students ◽  
Education For Sustainable Development ◽  
Academic Education ◽  
Educational Activities ◽  
Geographical Education ◽  
Made In

Abstract The paper presents the topic of academic education for sustainable development (ESD). A diagnostic survey was made in a form of a questionnaire in three groups of respondents: active geography teachers, participants of postgraduate program preparing for teaching geography and undergraduate students majoring in geography. The conducted research revealed how the groups of respondents differ in regards perception and preparedness to use of SD and ESD in school geographical education

Frictional Vibrations

1955 ◽  
Vol 22 (2) ◽  
pp. 207-214
Author(s):  
David Sinclair
Keyword(s):  
Coefficient Of Friction ◽  
Equations Of Motion ◽  
Static Friction ◽  
Uniform Motion ◽  
Friction Characteristic ◽  
Stick Slip ◽  
The Coefficient Of Friction ◽  
Brake Lining ◽  
Solid Bodies ◽  
Frictional Vibrations

Abstract Frictional vibrations, such as stick-slip motion and automobile-brake squeal, which occur when two solid bodies are rubbed together, are analyzed mathematically and observed experimentally. The conditions studied are slow uniform motion and relatively rapid simple harmonic motion of brake lining over a cast-iron base. The equations of motion show and the observations confirm that frictional vibrations are caused primarily by an inverse variation of coefficient of friction with sliding velocity, but their form and occurrence are greatly dependent upon the dynamical constants of the mechanical system. With a constant coefficient of friction, the vibration initiated whenever sliding begins is rapidly damped out, not by the friction but by the “natural” damping of all mechanical systems. The coefficient of friction of most brake linings and other organic materials was essentially invariant with velocity, except that the static coefficient was usually greater than the sliding coefficient. Most such materials usually showed a small decrease in coefficient with increasing temperature. The persistent vibrations resulting from the excess static friction were reduced or eliminated by treating the rubbing surfaces with polar organic compounds which produced a rising friction characteristic.

On the Non-Linear Dynamics of a Traveling Cable With Small Sag

1995 ◽  
Author(s):  
Christoph G. Reuter ◽  
Peter Hagedorn
Keyword(s):  
Equations Of Motion ◽  
Steady State Solution ◽  
Extended Model ◽  
Transport Velocity ◽  
Non Linear ◽  
Mechanical Models ◽  
Linear Vibrations ◽  
Technical Systems ◽  
Inertia Forces ◽  
Made In

Abstract Traveling cables or threadlines appear in a number of technical applications such as textile machinery, V-belts, ski lifts, funiculars and also in simple models of traveling webs in paper machinery. The mechanical models used so far, most often neglect the effect of sag due to the weight of the cable, although it is well known that in some cases it may be quite important. In this paper, the authors develop a particularly simple model for translating cables using the assumption that the longitudinal inertia forces are negligible in comparison to the transversal inertia forces if the sag of the cable is sufficiently small. This assumption has already been made in a study of linear vibrations of stationary cables in 1970 by Irvine & Caughey. This lead to surprising results which have also been verified experimentally in the laboratory. The extended model presented in this paper includes gyroscopic and nonlinear terms in the equations of motion, related to the cable transport velocity and geometric nonlinearities. As a particular case (zero longitudinal speed and linear theory) the model of Irvine & Caughey is again contained in the present analysis. The linear and non-linear vibrations about a steady state solution are studied. The results show some interesting features which may also be relevant to technical systems if the transport speed is sufficiently high.

Analysis on Response of Blades With Friction Damping Interconnection Using a New Friction Model

1997 ◽  
Author(s):  
Zili Xu ◽  
Xinyi Li ◽  
Qingji Meng
Keyword(s):  
Equations Of Motion ◽  
Static Friction ◽  
Normal Pressure ◽  
Friction Model ◽  
Force Frequency ◽  
Steam Turbines ◽  
Friction Damping ◽  
Blade Vibration ◽  
Blade System ◽  
The Difference

Blades with damper structures have been widely used in gas and steam turbines. Operation experience indicate that damper structures can reduce the dynamic stress of the blade effectively, so it is essential to predict the oscillating characteristics of damped blade accurately. In this paper, a modified Oden friction model, which can consider the difference between static friction and dynamic friction, for analyzing nonlinear friction damping, is presented and the dynamic equations of motion of blade system is given also. The response of blade group with 5 blades is analyzed using the model presented in this paper. Factors such as the placement of connectors, external exciting force frequency, and normal pressure that influence the blade vibration characteristic are studied. Some results available for reference have been obtained.

Development of lying to conceal a transgression: Children’s control of expressive behaviour during verbal deception

2002 ◽  
Vol 26 (5) ◽  
pp. 436-444 ◽  
Author(s):  
Victoria Talwar ◽  
Kang Lee
Keyword(s):  
Undergraduate Students ◽  
Older Children ◽  
Video Clips ◽  
Leakage Control ◽  
Made In

The present study examined lying behaviour in children between 3 and 7 years of age with two experiments. A temptation resistance paradigm was used in which children were left alone in a room with a music-playing toy placed behind their back. The children were told not to peek at the toy. Most children could not resist the temptation and peeked at the toy. When the experimenter asked them whether they had peeked, about half of the 3-year-olds confessed to their transgression, whereas most older children lied. Näve adult evaluators (undergraduate students and parents) who watched video clips of the children’s responses could not discriminate lie-tellers from nonliars on the basis of their nonverbal expressive behaviours. However, the children were poor at semantic leakage control and adults could correctly identify most of the lie-tellers based on their verbal statements made in the same context as the lie. The combined results regarding children’s verbal and nonverbal leakage control suggest that children under 8 years of age are not fully skilled lie-tellers.

Constrained Multibody Dynamics With Python: From Symbolic Equation Generation to Publication

2013 ◽  
Author(s):  
Gilbert Gede ◽  
Dale L. Peterson ◽  
Angadh S. Nanjangud ◽  
Jason K. Moore ◽  
Mont Hubbard
Keyword(s):  
Open Source ◽  
Undergraduate Students ◽  
Multibody Systems ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Academic Research ◽  
General Purpose ◽  
Engineering Software ◽  
Symbolic Equations Of Motion ◽  
High Level

Symbolic equations of motion (EOMs) for multibody systems are desirable for simulation, stability analyses, control system design, and parameter studies. Despite this, the majority of engineering software designed to analyze multibody systems are numeric in nature (or present a purely numeric user interface). To our knowledge, none of the existing software packages are 1) fully symbolic, 2) open source, and 3) implemented in a popular, general, purpose high level programming language. In response, we extended SymPy (an existing computer algebra system implemented in Python) with functionality for derivation of symbolic EOMs for constrained multibody systems with many degrees of freedom. We present the design and implementation of the software and cover the basic usage and workflow for solving and analyzing problems. The intended audience is the academic research community, graduate and advanced undergraduate students, and those in industry analyzing multibody systems. We demonstrate the software by deriving the EOMs of a N-link pendulum, show its capabilities for LATEX output, and how it integrates with other Python scientific libraries — allowing for numerical simulation, publication quality plotting, animation, and online notebooks designed for sharing results. This software fills a unique role in dynamics and is attractive to academics and industry because of its BSD open source license which permits open source or commercial use of the code.

Sign in / Sign up

Export Citation Format

Share Document