A Physical Pendulum with Damping Due to Sliding Friction
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Chapter 7. the Principle of Least Action
Chapter 7. The Principle of Least Action 7.1 Force Methods vs. Energy Methods We have so far studied two distinct ways of analyzing physics problems: force methods, basically consisting of the application of Newton’s Laws, and energy methods, consisting of the application of the principle of conservation of energy (the conservations of linear and angular momenta can also be considered as part of this). Both have their advantages and disadvantages. More precisely, energy methods often involve scalar quantities (e.g., work, kinetic energy, and potential energy) and are thus easier to handle than forces, which are vectorial in nature. However, forces tell us more. The simple example of a particle subjected to the earth’s gravitation field will clearly illustrate this. We know that when a particle moves from position y0 to y in the earth’s gravitational field, the conservation of energy tells us that ΔK + ΔUgrav = 0 (7.1) 1 2 2 m v − v0 + mg(y − y0 ) = 0, 2 ( ) which implies that the final speed of the particle, of mass m , is 2 v = v0 + 2g(y0 − y). (7.2) Although we know the final speed v of the particle, given its initial speed v0 and the initial and final positions y0 and y , we do not know how its position and velocity (and its speed) evolve with time. On the other hand, if we apply Newton’s Second Law, then we write −mgey = maey dv (7.3) = m e . dt y This equation is easily manipulated to yield t v = dv ∫t0 t = − gdτ + v0 (7.4) ∫t0 = −g(t − t0 ) + v0 , - 138 - where v0 is the initial velocity (it appears in equation (7.4) as a constant of integration). -
Dynamics of the Elastic Pendulum Qisong Xiao; Shenghao Xia ; Corey Zammit; Nirantha Balagopal; Zijun Li Agenda
Dynamics of the Elastic Pendulum Qisong Xiao; Shenghao Xia ; Corey Zammit; Nirantha Balagopal; Zijun Li Agenda • Introduction to the elastic pendulum problem • Derivations of the equations of motion • Real-life examples of an elastic pendulum • Trivial cases & equilibrium states • MATLAB models The Elastic Problem (Simple Harmonic Motion) 푑2푥 푑2푥 푘 • 퐹 = 푚 = −푘푥 = − 푥 푛푒푡 푑푡2 푑푡2 푚 • Solve this differential equation to find 푥 푡 = 푐1 cos 휔푡 + 푐2 sin 휔푡 = 퐴푐표푠(휔푡 − 휑) • With velocity and acceleration 푣 푡 = −퐴휔 sin 휔푡 + 휑 푎 푡 = −퐴휔2cos(휔푡 + 휑) • Total energy of the system 퐸 = 퐾 푡 + 푈 푡 1 1 1 = 푚푣푡2 + 푘푥2 = 푘퐴2 2 2 2 The Pendulum Problem (with some assumptions) • With position vector of point mass 푥 = 푙 푠푖푛휃푖 − 푐표푠휃푗 , define 푟 such that 푥 = 푙푟 and 휃 = 푐표푠휃푖 + 푠푖푛휃푗 • Find the first and second derivatives of the position vector: 푑푥 푑휃 = 푙 휃 푑푡 푑푡 2 푑2푥 푑2휃 푑휃 = 푙 휃 − 푙 푟 푑푡2 푑푡2 푑푡 • From Newton’s Law, (neglecting frictional force) 푑2푥 푚 = 퐹 + 퐹 푑푡2 푔 푡 The Pendulum Problem (with some assumptions) Defining force of gravity as 퐹푔 = −푚푔푗 = 푚푔푐표푠휃푟 − 푚푔푠푖푛휃휃 and tension of the string as 퐹푡 = −푇푟 : 2 푑휃 −푚푙 = 푚푔푐표푠휃 − 푇 푑푡 푑2휃 푚푙 = −푚푔푠푖푛휃 푑푡2 Define 휔0 = 푔/푙 to find the solution: 푑2휃 푔 = − 푠푖푛휃 = −휔2푠푖푛휃 푑푡2 푙 0 Derivation of Equations of Motion • m = pendulum mass • mspring = spring mass • l = unstreatched spring length • k = spring constant • g = acceleration due to gravity • Ft = pre-tension of spring 푚푔−퐹 • r = static spring stretch, 푟 = 푡 s 푠 푘 • rd = dynamic spring stretch • r = total spring stretch 푟푠 + 푟푑 Derivation of Equations of Motion -
SMU PHYSICS 1303: Introduction to Mechanics
SMU PHYSICS 1303: Introduction to Mechanics Stephen Sekula1 1Southern Methodist University Dallas, TX, USA SPRING, 2019 S. Sekula (SMU) SMU — PHYS 1303 SPRING, 2019 1 Outline Conservation of Energy S. Sekula (SMU) SMU — PHYS 1303 SPRING, 2019 2 Conservation of Energy Conservation of Energy NASA, “Hipnos” by Molinos de Viento and available under Creative Commons from Flickr S. Sekula (SMU) SMU — PHYS 1303 SPRING, 2019 3 Conservation of Energy Key Ideas The key ideas that we will explore in this section of the course are as follows: I We will come to understand that energy can change forms, but is neither created from nothing nor entirely destroyed. I We will understand the mathematical description of energy conservation. I We will explore the implications of the conservation of energy. Jacques-Louis David. “Portrait of Monsieur de Lavoisier and his Wife, chemist Marie-Anne Pierrette Paulze”. Available under Creative Commons from Flickr. S. Sekula (SMU) SMU — PHYS 1303 SPRING, 2019 4 Conservation of Energy Key Ideas The key ideas that we will explore in this section of the course are as follows: I We will come to understand that energy can change forms, but is neither created from nothing nor entirely destroyed. I We will understand the mathematical description of energy conservation. I We will explore the implications of the conservation of energy. Jacques-Louis David. “Portrait of Monsieur de Lavoisier and his Wife, chemist Marie-Anne Pierrette Paulze”. Available under Creative Commons from Flickr. S. Sekula (SMU) SMU — PHYS 1303 SPRING, 2019 4 Conservation of Energy Key Ideas The key ideas that we will explore in this section of the course are as follows: I We will come to understand that energy can change forms, but is neither created from nothing nor entirely destroyed. -
Measuring Earth's Gravitational Constant with a Pendulum
Measuring Earth’s Gravitational Constant with a Pendulum Philippe Lewalle, Tony Dimino PHY 141 Lab TA, Fall 2014, Prof. Frank Wolfs University of Rochester November 30, 2014 Abstract In this lab we aim to calculate Earth’s gravitational constant by measuring the period of a pendulum. We obtain a value of 9.79 ± 0.02m/s2. This measurement agrees with the accepted value of g = 9.81m/s2 to within the precision limits of our procedure. Limitations of the techniques and assumptions used to calculate these values are discussed. The pedagogical context of this example report for PHY 141 is also discussed in the final remarks. 1 Theory The gravitational acceleration g near the surface of the Earth is known to be approximately constant, disregarding small effects due to geological variations and altitude shifts. We aim to measure the value of that acceleration in our lab, by observing the motion of a pendulum, whose motion depends both on g and the length L of the pendulum. It is a well known result that a pendulum consisting of a point mass and attached to a massless rod of length L obeys the relationship shown in eq. (1), d2θ g = − sin θ, (1) dt2 L where θ is the angle from the vertical, as showng in Fig. 1. For small displacements (ie small θ), we make a small angle approximation such that sin θ ≈ θ, which yields eq. (2). d2θ g = − θ (2) dt2 L Eq. (2) admits sinusoidal solutions with an angular frequency ω. We relate this to the period T of oscillation, to obtain an expression for g in terms of the period and length of the pendulum, shown in eq. -
Sliding and Rolling: the Physics of a Rolling Ball J Hierrezuelo Secondary School I B Reyes Catdicos (Vdez- Mdaga),Spain and C Carnero University of Malaga, Spain
Sliding and rolling: the physics of a rolling ball J Hierrezuelo Secondary School I B Reyes Catdicos (Vdez- Mdaga),Spain and C Carnero University of Malaga, Spain We present an approach that provides a simple and there is an extra difficulty: most students think that it adequate procedure for introducing the concept of is not possible for a body to roll without slipping rolling friction. In addition, we discuss some unless there is a frictional force involved. In fact, aspects related to rolling motion that are the when we ask students, 'why do rolling bodies come to source of students' misconceptions. Several rest?, in most cases the answer is, 'because the didactic suggestions are given. frictional force acting on the body provides a negative acceleration decreasing the speed of the Rolling motion plays an important role in many body'. In order to gain a good understanding of familiar situations and in a number of technical rolling motion, which is bound to be useful in further applications, so this kind of motion is the subject of advanced courses. these aspects should be properly considerable attention in most introductory darified. mechanics courses in science and engineering. The outline of this article is as follows. Firstly, we However, we often find that students make errors describe the motion of a rigid sphere on a rigid when they try to interpret certain situations related horizontal plane. In this section, we compare two to this motion. situations: (1) rolling and slipping, and (2) rolling It must be recognized that a correct analysis of rolling without slipping. -
Coupling Effect of Van Der Waals, Centrifugal, and Frictional Forces On
PCCP View Article Online PAPER View Journal | View Issue Coupling effect of van der Waals, centrifugal, and frictional forces on a GHz rotation–translation Cite this: Phys. Chem. Chem. Phys., 2019, 21,359 nano-convertor† Bo Song,a Kun Cai, *ab Jiao Shi, ad Yi Min Xieb and Qinghua Qin c A nano rotation–translation convertor with a deformable rotor is presented, and the dynamic responses of the system are investigated considering the coupling among the van der Waals (vdW), centrifugal and frictional forces. When an input rotational frequency (o) is applied at one end of the rotor, the other end exhibits a translational motion, which is an output of the system and depends on both the geometry of the system and the forces applied on the deformable part (DP) of the rotor. When centrifugal force is Received 25th September 2018, stronger than vdW force, the DP deforms by accompanying the translation of the rotor. It is found that Accepted 26th November 2018 the translational displacement is stable and controllable on the condition that o is in an interval. If o DOI: 10.1039/c8cp06013d exceeds an allowable value, the rotor exhibits unstable eccentric rotation. The system may collapse with the rotor escaping from the stators due to the strong centrifugal force in eccentric rotation. In a practical rsc.li/pccp design, the interval of o can be found for a system with controllable output translation. 1 Introduction components.18–22 Hertal et al.23 investigated the significant deformation of carbon nanotubes (CNTs) by surface vdW forces With the rapid development in nanotechnology, miniaturization that were generated between the nanotube and the substrate. -
SEISMIC ANALYSIS of SLIDING STRUCTURES BROCHARD D.- GANTENBEIN F. CEA Centre D'etudes Nucléaires De Saclay, 91
n 9 COMMISSARIAT A L'ENERGIE ATOMIQUE CENTRE D1ETUDES NUCLEAIRES DE 5ACLAY CEA-CONF —9990 Service de Documentation F9II9I GIF SUR YVETTE CEDEX Rl SEISMIC ANALYSIS OF SLIDING STRUCTURES BROCHARD D.- GANTENBEIN F. CEA Centre d'Etudes Nucléaires de Saclay, 91 - Gif-sur-Yvette (FR). Dept. d'Etudes Mécaniques et Thermiques Communication présentée à : SMIRT 10.' International Conference on Structural Mechanics in Reactor Technology Anaheim, CA (US) 14-18 Aug 1989 SEISHIC ANALYSIS OF SLIDING STRUCTURES D. Brochard, F. Gantenbein C.E.A.-C.E.N. Saclay - DEHT/SMTS/EHSI 91191 Gif sur Yvette Cedex 1. INTRODUCTION To lirait the seism effects, structures may be base isolated. A sliding system located between the structure and the support allows differential motion between them. The aim of this paper is the presentation of the method to calculate the res- ponse of the structure when the structure is represented by its elgenmodes, and the sliding phenomenon by the Coulomb friction model. Finally, an application to a simple structure shows the influence on the response of the main parameters (friction coefficient, stiffness,...). 2. COULOMB FRICTION HODEL Let us consider a stiff mass, layed on an horizontal support and submitted to an external force Fe (parallel to the support). When Fg is smaller than a limit force ? p there is no differential motion between the support and the mass and the friction force balances the external force. The limit force is written: Fj1 = \x Fn where \i is the friction coefficient and Fn the modulus of the normal force applied by the mass to the support (in this case, Fn is equal to the weight of the mass). -
Friction Physics Terms
Friction Physics terms • coefficient of friction • static friction • kinetic friction • rolling friction • viscous friction • air resistance Equations kinetic friction static friction rolling friction Models for friction The friction force is approximately equal to the normal force multiplied by a coefficient of friction. What is friction? Friction is a “catch-all” term that collectively refers to all forces which act to reduce motion between objects and the matter they contact. Friction often transforms the energy of motion into thermal energy or the wearing away of moving surfaces. Kinetic friction Kinetic friction is sliding friction. It is a force that resists sliding or skidding motion between two surfaces. If a crate is dragged to the right, friction points left. Friction acts in the opposite direction of the (relative) motion that produced it. Friction and the normal force Which takes more force to push over a rough floor? The board with the bricks, of course! The simplest model of friction states that frictional force is proportional to the normal force between two surfaces. If this weight triples, then the normal force also triples—and the force of friction triples too. A model for kinetic friction The force of kinetic friction Ff between two surfaces equals the coefficient of kinetic friction times the normal force . μk FN direction of motion The coefficient of friction is a constant that depends on both materials. Pairs of materials with more friction have a higher μk. ● Basically the μk tells you how many newtons of friction you get per newton of normal force. A model for kinetic friction The coefficient of friction μk is typically between 0 and 1. -
Probing Biomechanical Properties with a Centrifugal Force Quartz Crystal Microbalance
ARTICLE Received 13 Nov 2013 | Accepted 17 Sep 2014 | Published 21 Oct 2014 DOI: 10.1038/ncomms6284 Probing biomechanical properties with a centrifugal force quartz crystal microbalance Aaron Webster1, Frank Vollmer1 & Yuki Sato2 Application of force on biomolecules has been instrumental in understanding biofunctional behaviour from single molecules to complex collections of cells. Current approaches, for example, those based on atomic force microscopy or magnetic or optical tweezers, are powerful but limited in their applicability as integrated biosensors. Here we describe a new force-based biosensing technique based on the quartz crystal microbalance. By applying centrifugal forces to a sample, we show it is possible to repeatedly and non-destructively interrogate its mechanical properties in situ and in real time. We employ this platform for the studies of micron-sized particles, viscoelastic monolayers of DNA and particles tethered to the quartz crystal microbalance surface by DNA. Our results indicate that, for certain types of samples on quartz crystal balances, application of centrifugal force both enhances sensitivity and reveals additional mechanical and viscoelastic properties. 1 Max Planck Institute for the Science of Light, Gu¨nther-Scharowsky-Str. 1/Bau 24, D-91058 Erlangen, Germany. 2 The Rowland Institute at Harvard, Harvard University, 100 Edwin H. Land Boulevard, Cambridge, Massachusetts 02142, USA. Correspondence and requests for materials should be addressed to A.W. (email: [email protected]). NATURE COMMUNICATIONS | 5:5284 | DOI: 10.1038/ncomms6284 | www.nature.com/naturecommunications 1 & 2014 Macmillan Publishers Limited. All rights reserved. ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/ncomms6284 here are few experimental techniques that allow the study surface of the crystal. -
Conservation of Linear Momentum: the Ballistic Pendulum
Conservation of Linear Momentum: the Ballistic Pendulum I. Discussion a. Determination of Velocity from Collision In the typical use made of a ballistic pendulum, a projectile, having a small mass, m, and a horizontal velocity, v, strikes and imbeds itself in a pendulum bob, having a large mass, M, and an initial horizontal velocity of zero. Immediately after the collision occurs the combined mass, M + m, of the bob and projectile has a small horizontal velocity, V. During this collision the conservation of linear momentum holds. If rotational effects are ignored, and if it is assumed that the time required for this event to take place is too short to allow the projectile to be substantially influenced by the earth's gravitational field, the motion remains horizontal, and mv = ( M + m ) V (1) After the collision has occurred, the combined mass, (M + m), rises along a circular arc to a vertical height h in the earth's gravitational field, as shown in Fig. l (c). During this portion of the motion, but not during the collision itself, the conservation of energy holds, if it is assumed that the effects of friction are negligible. Then, for motion along the arc, 1 2 ( M + m ) V = ( M + m) gh , or (2) 2 V = 2 gh (3) When V is eliminated using equations 1 and 3, the velocity of the projectile is v = M + m 2 gh (4) m b. Determination of Velocity from Range When a projectile, having an initial horizontal velocity, v, is fired from a height H above a plane, its horizontal range, R, is given by R = v t x o (5) and the height H is given by 1 2 H = gt (6) 2 where t = time during which projectile is in flight. -
Leonhard Euler - Wikipedia, the Free Encyclopedia Page 1 of 14
Leonhard Euler - Wikipedia, the free encyclopedia Page 1 of 14 Leonhard Euler From Wikipedia, the free encyclopedia Leonhard Euler ( German pronunciation: [l]; English Leonhard Euler approximation, "Oiler" [1] 15 April 1707 – 18 September 1783) was a pioneering Swiss mathematician and physicist. He made important discoveries in fields as diverse as infinitesimal calculus and graph theory. He also introduced much of the modern mathematical terminology and notation, particularly for mathematical analysis, such as the notion of a mathematical function.[2] He is also renowned for his work in mechanics, fluid dynamics, optics, and astronomy. Euler spent most of his adult life in St. Petersburg, Russia, and in Berlin, Prussia. He is considered to be the preeminent mathematician of the 18th century, and one of the greatest of all time. He is also one of the most prolific mathematicians ever; his collected works fill 60–80 quarto volumes. [3] A statement attributed to Pierre-Simon Laplace expresses Euler's influence on mathematics: "Read Euler, read Euler, he is our teacher in all things," which has also been translated as "Read Portrait by Emanuel Handmann 1756(?) Euler, read Euler, he is the master of us all." [4] Born 15 April 1707 Euler was featured on the sixth series of the Swiss 10- Basel, Switzerland franc banknote and on numerous Swiss, German, and Died Russian postage stamps. The asteroid 2002 Euler was 18 September 1783 (aged 76) named in his honor. He is also commemorated by the [OS: 7 September 1783] Lutheran Church on their Calendar of Saints on 24 St. Petersburg, Russia May – he was a devout Christian (and believer in Residence Prussia, Russia biblical inerrancy) who wrote apologetics and argued Switzerland [5] forcefully against the prominent atheists of his time. -
Newton Laws (Friction Forces)
Lecture 8 Physics I Chapter 6 Newton Laws (Friction forces) I am greater than Newton Course website: https://sites.uml.edu/andriy-danylov/teaching/physics-i/ PHYS.1410 Lecture 8 Danylov Department of Physics and Applied Physics Today we are going to discuss: Chapter 6: Newton 1st and 2nd Laws Kinetic/Static Friction: Section 6.4 PHYS.1410 Lecture 8 Danylov Department of Physics and Applied Physics Newton’s laws In 1687 Newton published his three laws in his Principia Mathematica. These intuitive laws are remarkable intellectual achievements and work spectacular for everyday physics PHYS.1410 Lecture 8 Danylov Department of Physics and Applied Physics Newton’s 1st Law (Law of Inertia) In the absence of force, objects continue in their state of rest or of uniform velocity in a straight line i.e. objects want to keep on doing what they are already doing - It helps to find inertial reference frames, where Newton 2nd Law has that famous simple form F=ma PHYS.1410 Lecture 8 Danylov Department of Physics and Applied Physics Inertial reference frame Inertial reference frame – A reference frame at rest – Or one that moves with a constant velocity An inertial reference frame is one in which Newton’s first law is valid. This excludes rotating and accelerating frames (non‐inertial reference frames), where Newton’s first law does not hold. How can we tell if we are in an inertial reference frame? ‐ By checking if Newton’s first law holds! All our problems will be solved using inertial reference frames PHYS.1410 Lecture 8 Danylov Department of Physics and Applied Physics Example Inertial Reference Frame A physics student cruises at a constant velocity in an airplane.