Reply to Professor Simon’s comments

1952 ◽  
Vol 212 (1111) ◽  
pp. 477-477
Keyword(s):  
Free Energy ◽  
Potential Energy ◽  
Temperature Rise ◽  
Frictional Resistance ◽  
Mechanical Equivalent ◽  
Work Of Deformation ◽  
Work Done

The question raised by Professor Simon on the mechanism by which the work done against the frictional resistance is transformed into heat perhaps requires a more fundamental explanation than can be deduced from frictional experiments alone. I t is true that free energy is required for the formation of a new surface when the intermetallic junctions are ruptured, and this in itself does not produce an appreciable temperature rise. With plastic solids (as distinct from liquids), however, most of the work is required to deform the metal around the junctions. As Taylor & Quinney (1937) have shown at least 90% of the work of deformation is liberated as heat and less than 10 % remains as potential energy in the deformed metal, but if the metal is already heavily deformed the proportion of potential energy retained in the metal is negligibly small. Some of the early determinations of the mechanical equivalent of heat are of course based on the assumption that all the frictional work appears as heat. I would like to ask Dr A. J. W. Moore to comment further on this.

Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

2021 ◽  
Vol 57 (1) ◽  
pp. 015012
Author(s):  
Unofre B Pili ◽  
Renante R Violanda
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Conservation Law ◽  
Gravitational Potential Energy ◽  
Time Data ◽  
Home Based ◽  
Basic Physics ◽  
Free Falling ◽  
Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

Variational thermodynamic derivation of the formula for pressure difference across a charged conducting liquid surface and its relation to the thermodynamics of electrical capacitance

1995 ◽  
Vol 450 (1938) ◽  
pp. 177-192 ◽  
Keyword(s):  
Free Energy ◽  
Pressure Difference ◽  
Liquid Surface ◽  
Field Energy ◽  
Conducting Liquid ◽  
Difference Formula ◽  
Direct Energy ◽  
Free Case ◽  
Definition Of ◽  
Work Done

The formula for pressure difference across a charged conducting liquid surface has conventionally been derived by adding a Maxwell stress term to the pressure-difference formula for the field-free case. As far as can be established, no derivation applying direct energy-based methods to the charged-surface case has ever been clearly formulated. This paper presents a first-principles variational derivation, starting from the laws of thermodynamics and modelled on Gibbs’s (1875) approach to the field-free case. The derivation applies to the static equilibrium situation. The method is to treat the charged liquid and its environment as a heterogeneous system in thermodynamic equilibrium, and consider the effects of a small virtual variation in the shape of the conducting-liquid surface. Expressions can be obtained for virtual changes in the free energies of relevant system components and for the virtual electrical work done on the system. By converting the space integral of the variation in electrostatic field energy to an integral over the surface of the liquid electrode, the usual pressure-difference formula is retrieved. It is also shown how the problem can be formulated, in various ways, as a free-energy problem in a situation involving electric stresses and capacitance. The most satisfactory approach involves the definition of an unfamiliar form of free energy, that can be seen as the electrical analogue of the Gibbs free energy and may have use in other contexts.

scholarly journals Simulation of FUS protein condensates with an adapted coarse-grained model

2020 ◽  
Author(s):  
Zakarya Benayad ◽  
Sören von Bülow ◽  
Lukas S. Stelzl ◽  
Gerhard Hummer
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Potential Energy ◽  
Energy Function ◽  
Potential Energy Function ◽  
Scaling Factor ◽  
Coarse Grained ◽  
Disordered Proteins ◽  
General Strategy ◽  
Droplet Shape

AbstractDisordered proteins and nucleic acids can condense into droplets that resemble the membraneless organelles observed in living cells. MD simulations offer a unique tool to characterize the molecular interactions governing the formation of these biomolecular condensates, their physico-chemical properties, and the factors controlling their composition and size. However, biopolymer condensation depends sensitively on the balance between different energetic and entropic contributions. Here, we develop a general strategy to fine-tune the potential energy function for molecular dynamics simulations of biopolymer phase separation. We rebalance protein-protein interactions against solvation and entropic contributions to match the excess free energy of transferring proteins between dilute solution and condensate. We illustrate this formalism by simulating liquid droplet formation of the FUS low complexity domain (LCD) with a rebalanced MARTINI model. By scaling the strength of the nonbonded interactions in the coarse-grained MARTINI potential energy function, we map out a phase diagram in the plane of protein concentration and interaction strength. Above a critical scaling factor of αc ≈ 0.6, FUS LCD condensation is observed, where α = 1 and 0 correspond to full and repulsive interactions in the MARTINI model, respectively. For a scaling factor α = 0.65, we recover the experimental densities of the dilute and dense phases, and thus the excess protein transfer free energy into the droplet and the saturation concentration where FUS LCD condenses. In the region of phase separation, we simulate FUS LCD droplets of four different sizes in stable equilibrium with the dilute phase and slabs of condensed FUS LCD for tens of microseconds, and over one millisecond in aggregate. We determine surface tensions in the range of 0.01 to 0.4mN/m from the fluctuations of the droplet shape and from the capillary-wave-like broadening of the interface between the two phases. From the dynamics of the protein end-to-end distance, we estimate shear viscosities from 0.001 to 0.02Pas for the FUS LCD droplets with scaling factors α in the range of 0.625 to 0.75, where we observe liquid droplets. Significant hydration of the interior of the droplets keeps the proteins mobile and the droplets fluid.

scholarly journals Transition Energy, Orientation Force and Work Done in Transitional Behavior Atoms: Formulating New Principles in Thermodynamics

2020 ◽  
Author(s):  
Mubarak Ali
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Transition Energy ◽  
Condensed Matter ◽  
Ground Surface ◽  
First Law Of Thermodynamics ◽  
Transitional Behavior ◽  
Liquid States ◽  
Physical And Chemical ◽  
Work Done

<p></p><p>A study of different parameters in thermodynamics is important for sustainable science behind physical and chemical phenomena. This study finds anomaly associated with the first law of thermodynamics. The anomaly is resolved for the equations of change in the internal energy of a system composed of atoms. A gas atom involves transitional energy gained to undertake transition state. Hence, the work is carried out by that gas atom. This can be registered symbolically in a plus form. A solid atom involves transitional energy absorbed to undertake transition state. Hence, the work is carried out on that solid atom, which can be registered in a minus form. At typical level of a ground surface, atoms give birth to condensed matter physics, so<b> </b>atoms of solid behaviors should also give birth to transition matter physics. In a system composed of gas or solid atoms, varying energy and force introduce different transition states. Orientational force of an electron either in the transition of gas atom or in the transition of solid atom is by varying potential energy under transitional energy. Thus, understandable concepts of cooling and heating are deduced from their respective gas atoms and solid atoms when they are recovered from their attained liquid states.</p><p></p>

scholarly journals Transition Energy, Orientation Force and Work Done in Transitional Behavior Atoms; Formulating New Principles in Thermodynamics

2020 ◽  
Author(s):  
Mubarak Ali
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Transition Energy ◽  
Condensed Matter ◽  
Ground Surface ◽  
First Law Of Thermodynamics ◽  
Transitional Behavior ◽  
Liquid States ◽  
Physical And Chemical ◽  
Work Done

<p>Study of different parameters in thermodynamics is important for sustainable science behind physical and chemical phenomena. This study finds anomaly associated with the first law of thermodynamics. The anomaly is resolved for the equations of change in internal energy of a system composed of atoms. A gas atom involves transition energy gained to undertake transition state. Hence, work done is carried out by that gas atom. Symbolically, this can be registered in plus form. However, a solid atom involves transition energy absorbed to undertake transition state. Hence, work done is carried out on that solid atom, which can be registered in minus form. At typical level ground surface, atoms give birth to condensed matter physics, so<b> </b>atoms of solid behaviors should also give birth to transition matter physics. In a system composed of gas or solid atoms, varying energy and force introduce different transition states. Orientation force of an electron either in transition of gas atom or in transition of solid atom is by varying potential energy under transition energy. So, understandable concepts of cooling and heating are deduced from respective gas atoms and solid atoms when recovering from their liquid states. </p>

Surfaces, Interfaces, and Changing Shapes in Multilayered Films

MRS Bulletin ◽  
1999 ◽  
Vol 24 (2) ◽  
pp. 39-43 ◽  
Author(s):  
Daniel Josell ◽  
Frans Spaepen
Keyword(s):  
Free Energy ◽  
Excess Free Energy ◽  
External Pressure ◽  
Electronic Density ◽  
Spherical Drop ◽  
Crystal Anisotropy ◽  
Fundamental Quantity ◽  
The Difference ◽  
Image Position ◽  
Work Done

It is generally recognized that the capillary forces associated with internal and external interfaces affect both the shapes of liquid-vapor surfaces and wetting of a solid by a liquid. It is less commonly understood that the same phenomenology often applies equally well to solid-solid or solid-vapor interfaces.The fundamental quantity governing capillary phenomena is the excess free energy associated with a unit area of interface. The microscopic origin of this excess free energy is often intuitively simple to understand: the atoms at a free surface have “missing bonds”; a grain boundary contains “holes” and hence does not have the optimal electronic density; an incoherent interface contains dislocations that cost strain energy; and the ordering of a liquid near a solid-liquid interface causes a lowering of the entropy and hence an increase in the free energy. In what follows we shall show how this fundamental quantity determines the shape of increasingly complex bodies: spheres, wires, thin films, and multilayers composed of liquids or solids. Crystal anisotropy is not considered here; all interfaces and surfaces are assumed isotropic.Consideration of the equilibrium of a spherical drop of radius R with surface free energy γ shows that pressure inside the droplet is higher than outside. The difference is given by the well-known Laplace equation:This result can be obtained by equating work done against internal and external pressure during an infinitesimal change of radius with the work of creating a new surface.

Comments on the energetics of the frictional process

1952 ◽  
Vol 212 (1111) ◽  
pp. 477-477
Keyword(s):  
Free Energy ◽  
Potential Energy ◽  
Rolling Friction ◽  
External Friction ◽  
Main Process ◽  
Final Question

I would like to ask what in Dr Bowden’s picture is the mechanism by which the free energy is transformed into heat ? If I understood him rightly, the free energy is needed for the breaking of bonds, but this does not produce heat. Could he tell us a little more about this ? Also I would like to know whether exact measurements have ever been made on the process of dry external friction to show what percentage of the energy is transformed into heat and what turns up in the form of potential energy stored in deformation of the material. A final question which may have some connexion with the first one: if the formation and breaking up of the bonds is the main process consuming energy, how does it come about that rolling friction is so much smaller than gliding friction ?

Free energy via thermostatted dynamic potential-energy changes

1993 ◽  
Vol 47 (6) ◽  
pp. 3852-3861 ◽  
Author(s):  
Brad Lee Holian ◽  
H. A. Posch ◽  
W. G. Hoover
Keyword(s):  
Free Energy ◽  
Potential Energy ◽  
Dynamic Potential
Sign in / Sign up

Export Citation Format

Share Document