Attraction and Repulsion
Attraction and repulsion are fundamental forces in physics that describe the interaction between objects. Attraction refers to the force that pulls objects together, such as gravity or the electromagnetic force between opposite charges. Repulsion, on the other hand, describes the force that pushes objects apart, like the electromagnetic force between like charges. These forces play a crucial role in understanding the behavior of particles and objects in the universe.
7 Key excerpts on "Attraction and Repulsion"
eBook - ePub- Aurelio Grande Rodríguez(Author)
- 2020(Publication Date)
- Editorial Autores de Argentina(Publisher)
...Attraction and Repulsion: If the forces of attraction didn´t exist in nature, solids would not exist, but if the forces of repulsion didn´t exist, neither would gases exist; everything seems to be a matter of measurement and organization to obtain the most appropriate relationship. Bodies attract each other but this condition is curiously selective, it happens that they never merge into the same and only block; if other opposing forces weren´t at work, particular things wouldn´t exist. Considering the composition, attractive forces act in each body to sustain the cohesion between its parts but at the same time, between them as individuals, a striking repulsion is also observed; in both cases to maintain the individuality of each system. They´re contrary actions of an ambiguous condition that, far from being balanced, behave in a suspicious way selective; about a very special phenomenology where sheer physical forces can´t explain this behavior. Gravitation, understood only as a positive force, can´t be justified as such in the face of the great variety of forms that as well as attract each other, they also reject each other. This paradoxical dynamic scenario is a process that, despite being physical, seems to be placed above the postulates of mechanics; as if that selectivity in the actions were a kind of construction will -that seeks to position itself on a situation that far exceeds the simplicity of the favorable. In living bodies, for example, attractive and repulsive forces are simultaneously brought into play that not only maintain shape, but also perform functions that require special plasticity...
eBook - ePub- Immanuel Kant, Delphi Classics(Authors)
- 2017(Publication Date)
- Delphi Classics (Parts Edition)(Publisher)
...For that whereby space is filled is substance, it is said, and this is correct enough. But as substance only reveals its existence to us by sense, whereby we perceive its impenetrability, namely by feeling — and therefore only in reference to contact, whose beginning (in the approach of one matter to another) is termed impact, but its continuation pressure — it seems as though the immediate effect of one matter on another could never be anything else but pressure or impact, the only two influences we can immediately feel; while on the other hand attraction, which can give us either no feeling at all, or at least no definite object of it, becomes difficult for us to conceive as fundamental force. Proposition 6. By mere attraction, without repulsion, no matter is possible. Demonstration. Attractive force is the moving force of matter, whereby it compels another [matter] to approach it; consequently, when it is met with, between all parts of matter, the matter seeks by means of it to diminish the distance of its parts from one another, and therefore the space that they together occupy. Now nothing can hinder the effect of a moving force, except another moving force opposed thereto, but this [force] that is opposed to it is repulsive force. Thus, without repulsive forces, and by mere approach, all parts of matter would approach one another without hindrance and diminish the space that they occupy. As now, in the case assumed, there is no distance of parts, in which a greater approach through attraction is rendered impossible by a repulsive force, they would move towards one another until no distance existed between them; that is, they would coalesce in a mathematical point, and the space would be empty; in other words, without any matter. Matter is accordingly impossible by mere attractive forces, without repulsive. Note. That property, on which the inner possibility of a thing rests as its condition, is an essential element therein...
eBook - ePub- Jacob N. Israelachvili(Author)
- 2010(Publication Date)
- Academic Press(Publisher)
...One may divide them into categories of “opposites”—in other words, attractive or repulsive, short-ranged or long-ranged, strong or weak, and isotropic or directional. These are important distinctions, but they are also ambiguous and confusing. A force that has the same physical origin may be both short-ranged and long-ranged, or it may be attractive in one solvent and repulsive in another. This way of classification can also result in the same force being “counted twice” in any theoretical analysis. To avoid such pitfalls, it is best to classify forces according to their different physical or chemical origin, although even here we shall see that the forces among large particles or extended surfaces lend themselves to different modes of classification from those occurring between two atoms or molecules; this is because the collective interaction of many molecules, which always includes entropic effects (see following), cannot be easily related to the individual pair potentials. First, some forces are purely electrostatic in origin, arising from the Coulomb force between charges. The interactions among charges, ions, permanent dipoles, quadrupoles, and so forth fall into this category. Electrostatic forces include polarization interactions that arise from the dipole moments induced in atoms and molecules by the electric fields of nearby charges and permanent dipoles. All electrostatic interactions in a solvent medium involve polarization effects. The electrostatic forces between electroneutral 2 molecules or assemblies that are free to mutually orient are generally attractive, and they occur even at zero temperature (T = 0 K). Second, some forces have a purely entropic origin. They arise from the collective behavior of molecules at finite temperatures (T > 0) and therefore cannot be described in terms of a pair potential or force-law between two molecules...
eBook - ePub- Alan Joel Witten(Author)
- 2017(Publication Date)
- Routledge(Publisher)
...2 Gravity: The Pull of the Earth Gravity is a force of mutual attraction between two masses and it will be shown here how this force can be exploited to detect and locate shallowly buried objects. Further discussions of gravitational force require more explanation of what is meant by force, mass, and other quantities, such as density, volume, acceleration, vectors, and scalars. These discussions will be presented throughout this chapter but, for the moment, consider the two masses, m and M, illustrated in Fig. 2.1 separated by a distance R. Figure 2.1. Geometry used in the definition of gravitational force. The gravitational force acting between these two masses is the product of the masses mM and varies inversely proportional to the square of their separation R. A very basic definition of force is a quantity that causes motion or a change in motion. Thus, a gravitational force can induce a motion in either of the two masses. It is impossible to determine if m is stationary and M moves towards m, M is stationary and m moves towards M, or both masses move towards each other. The perception of motion depends on the reference frame from which observations are being made. An intuitive example of this is the perception of motion within a moving train. Stationary objects outside of a moving train appear to be in motion when viewed from within the train. Although the train is in fact moving, it can appear stationary, with external objects moving when they are observed from a reference frame within the train. With geophysical measurements made on or near the surface of the Earth, it is assumed that the Earth is stationary and objects on or above its surface move towards it under the force of gravity. Thus, elevating an object above the surface of the Earth and subsequently releasing it will result in its 'falling' back to the surface of the Earth. Thus far, the discussion of gravity has been limited to forces between two masses...
eBook - ePubBasic Engineering Mechanics Explained, Volume 1
Principles and Static Forces
- Gregory Pastoll, Gregory Pastoll(Authors)
- 2019(Publication Date)
- Gregory Pastoll(Publisher)
...To understand this, we need to understand the connection between weight and gravity. Weight, Newton’s Law of Gravitation, and gravitational acceleration Isaac Newton, following the work of Robert Hooke, confirmed that a gravitational force exists between any two objects in the universe. Simply due to the fact that the objects have mass, they attract each other. This means that if two rocks are drifting in space, near one another, they will each exert a pull on the other, the result of which is that they will gradually accelerate towards one another. The more mass the two objects possess, the greater is this force. The further apart they are, the smaller is this force. Newton’s Law of Gravitation tell us that the magnitude of the gravitational force, F, depends on these variables, in the following relationship: F = (Gm 1 m 2)/r 2 Where G is the universal gravitation constant, m 1 and m 2 are the masses of the two objects, and r is the distance between their centres of gravity. This law applies to all bodies, not only to the gravitational force between a given object and the Earth. Every object that possesses mass attracts every other object with a force of attraction given by the above equation. It might be hard to believe that two pencils lying on your desk exert a gravitational pull on one another, but they do. The magnitude of this pull is insignificant, because both of their masses are vastly smaller than the mass of the earth. The magnitude of the gravitational force of attraction between two small objects was first determined in a famous experiment by the British scientist Henry Cavendish in 1797. A torsion wire suspended from an overhead beam supported a horizontal rod, on the ends of which were mounted two small lead spheres. When the rod had settled into an equilibrium position, two larger spheres were brought from a distance, to a position on the circle of movement close to the small ones, and equidistant from them...
eBook - ePubDevelopments in Surface Contamination and Cleaning, Vol. 1
Fundamentals and Applied Aspects
- Rajiv Kohli, Kashmiri L. Mittal, Rajiv Kohli, Kashmiri L. Mittal(Authors)
- 2015(Publication Date)
- William Andrew(Publisher)
...Let us consider, for example, the case of a spherical particle of radius R and mass density ρ at the surface of the earth. The gravitational force F g acting on such a particle is given by F g = 4 3 π ρ R 3 g (4.1) where g is the acceleration due to gravity and equals 9.8 m/s 2. For a particle with a radius of 5 μm and a density ρ = 1 g/cm 3, the gravitational force, F g, is ~ 5 × 10 − 12 N. While this force is quite small for this particle, its dependence on the cube of the radius implies that this force will increase rapidly with increasing particle size. The effect of gravity is shown in Figure 4.1. Figure 4.1 The gravitational, electrostatic, and van der Waals forces acting on a particle in contact with a substrate. Note how van der Waals interactions dominate for small particles, whereas gravity is the dominant force for large particles and electrostatic forces dominate for intermediate-size particles. Finally, let us consider the role of electromagnetic interactions in particle adhesion. To do so, however, requires that we further subdivide these interactions into magnetic, electrostatic, and electrodynamic interactions. Furthermore, let us first consider the role of magnetic interactions. Magnetic interactions are important for certain classes of materials that are of technological importance today, ranging from magnaflux devices used to detect cracks to magnetic recording materials to magnetic carriers used in electrophotographic engines to charge and transport the toner particles. Unfortunately, there has not been much research in the area of the adhesion of magnetic particles and this remains a rich field for enterprising scientists and engineers to explore. Let us now turn our attention to electrostatic interactions...
eBook - ePubSignposts to God
How Modern Physics and Astronomy Point the Way to Belief
- Peter Bussey(Author)
- 2016(Publication Date)
- IVP Academic(Publisher)
...The sun pulls on the planets, and so they continue to revolve in orbits around the sun. Today we are aware that all the stars in our galaxy pull on each other, and so the galaxy stays held together. Newton proposed a universal law of gravitation, stating that the gravitational force between any two objects is inversely proportional to the square of the distance between them. He was then able to prove that his laws could explain the orbits of the planets—a breakthrough in the understanding of astronomy. Gravity always pulls things toward each other in normal circumstances—it is an “attractive” force. We do not know of any way to make “antigravity,” such as would produce a repulsive force and free us from the earth. One of Albert Einstein’s great achievements was to devise a more all-embracing theory of gravity than Newton’s, one that relates gravitational acceleration to the structure of space and time. But not even Einstein’s theory, his “general theory of relativity,” gives a practical way to make antigravity, to the frustration of hopeful space travelers. FIRST DISCOVERIES IN ELECTRICITY AND MAGNETISM The word electricity first appeared in the English language in the seventeenth century, 1 although electric effects had been known about since ancient times. Electricity was originally known as a kind of force generated when suitable materials were rubbed together. Today we see this most easily by rubbing a plastic rod with a cloth; this can give it an electric charge, which makes it attract small pieces of paper or material so that they stick to it. The eighteenth century was an age of methodical scientific experiments, and gradually certain general properties of electricity became better known. The electricity associated with rubbed objects, later known as “static” electricity, could be transferred to other objects, and it behaved rather like a kind of substance that could be deposited on or removed from materials...
