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For other uses, see Force (disambiguation). Look up Force in Wiktionary, the free dictionary. In physics, force is that which can cause a mass to accelerate. It may be experienced as a lift, a push, or a pull. The acceleration of the body is proportional to the vector sum of all forces acting on it (known as net force or resultant force). In an extended body, force may also cause rotation, deformation, or an increase in pressure for the body. Rotational effects are determined by the torques, while deformation and pressure are determined by the stresses that the forces create. Force has several meanings: In physics, force is transforming(transporting) motion, as in F = m · a. ... Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... For other uses, see Mass (disambiguation). ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... A vector in physics and engineering typically refers to a quantity that has close relationship to the spatial coordinates, informally described as an object with a magnitude and a direction. The word vector is also now used for more general concepts (see also vector and generalizations below), but in this... This article is about vectors. ... This article is about rotation as a movement of a physical body. ... In engineering mechanics, deformation is a change in shape due to an applied force. ... This article is about pressure in the physical sciences. ... For other senses of this word, see torque (disambiguation). ... Stress is a measure of force per unit area within a body. ... Net force is mathematically equal to the time rate of change of the momentum of the body on which it acts. Since momentum is a vector quantity (has both a magnitude and direction), force also is a vector quantity. Look up time in Wiktionary, the free dictionary. ... In mathematics, the derivative of a function is one of the two central concepts of calculus. ... This article is about momentum in physics. ... This article is about momentum in physics. ... This article is about vectors that have a particular relation to the spatial coordinates. ... The concept of force has formed part of statics and dynamics since ancient times. Ancient contributions to statics culminated in the work of Archimedes in the 3rd century BC, which still forms part of modern physics. In contrast, Aristotle's dynamics incorporated intuitive misunderstandings of the role of force which were eventually corrected in the 17th century, culminating in the work of Isaac Newton. Following the development of quantum mechanics it is now understood that particles influence each another through fundamental interactions and therefore the standard model of particle physics demands that everything experienced fundamentally as a "force" is actually mediated by gauge bosons. Only four fundamental interactions are known: strong, electromagnetic, weak (unified into one electroweak interaction in 1970s), and gravitational (in order of decreasing strength). Statics is the branch of physics concerned with physical systems in static equilibrium, that is, in a state where the relative positions of subsystems do not vary over time, or where components and structures are at rest under the action of external forces of equilibrium. ... In physics, dynamics is the branch of classical mechanics that is concerned with the effects of forces on the motion of objects. ... For other uses, see Archimedes (disambiguation). ... The 3rd century BC started the first day of 300 BC and ended the last day of 201 BC. It is considered part of the Classical era, epoch, or historical period. ... For other uses, see Aristotle (disambiguation). ... (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... A fundamental interaction or fundamental force is a mechanism by which particles interact with each other, and which cannot be explained in terms of another interaction. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Gauge bosons are bosonic particles which act as carriers of the fundamental forces of Nature. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... This article covers the physics of gravitation. ... Contents 1 History 2 Describing forces 2.1 Static equilibrium 2.2 Dynamical equilibrium 2.3 Newtonian definitions 2.3.1 Newton's first law 2.3.2 Newton's second law 2.3.3 Newton's third law 3 Types of force 3.1 Gravity 3.2 Electromagnetic forces 3.3 Nuclear forces 4 Force and potential 4.1 Conservative forces 4.2 Nonconservative forces 5 Units of measurement 5.1 Conversions 6 Force in special relativity 7 See also 8 References [edit] History Aristotle famously described a force as anything which causes an object to undergo "unnatural motion" Aristotle and his followers believed that it was the natural state of massive objects on Earth (such as water and earth) to be motionless and that they tended towards that state if left alone. He distinguished between the innate tendency of objects to find their "natural place" (e.g. for heavy bodies to fall), which lead to "natural motion", and unnatural or forced motion, which required continued application of a force. But this theory, although based on the everyday experience of how objects move (e.g. constant application of a force to keep a cart moving), had severe trouble accounting for projectiles, such as the flight of arrows. Several theories were discussed over the centuries, and the late medieval idea that objects in forced motion carried an innate force of impetus was influential on the work of Galileo. Galileo constructed an experiment in which stones and cannonballs were both rolled down an incline to disprove the Aristotelian theory of motion early in the 17th century. He showed that the bodies were accelerated by gravity to an extent which was independent of their mass and argued that objects retain their velocity unless acted on by a force, for example friction. Image File history File links Metadata Size of this preview: 427 × 599 pixelsFull resolution (536 × 752 pixel, file size: 99 KB, MIME type: image/jpeg) This picture was already on Wikipedia, and under a usable copyright (see below in quotes). ... Image File history File links Metadata Size of this preview: 427 × 599 pixelsFull resolution (536 × 752 pixel, file size: 99 KB, MIME type: image/jpeg) This picture was already on Wikipedia, and under a usable copyright (see below in quotes). ... For other uses, see Aristotle (disambiguation). ... For other uses, see Aristotle (disambiguation). ... This article is about Earth as a planet. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... Inertia is the property of an object to remain at constant velocity unless acted upon by an outside force. ... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... The Aristotelian theory of gravity was that all bodies move towards their natural place. ... (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... For other uses, see Mass (disambiguation). ... This article is about velocity in physics. ... For other uses, see Friction (disambiguation). ... Isaac Newton is recognised as the person who argued explicitly for the first time that, in general, a constant force causes a constant rate of change (time derivative) of momentum. In essence, he gave the first (and the only) mathematical definition of the quantity force itself - as being the time-derivative of momentum: F = dp / dt. Newton went on to publish his Principia Mathematica which used concepts of inertia, force, and conservation to describe the motion of all objects. Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... A time derivative is a derivative of a function with respect to time, t. ... The Principia Mathematica is a three-volume work on the foundations of mathematics, written by Alfred North Whitehead and Bertrand Russell and published in 1910-1913. ... This article is about inertia as it applies to local motion. ... In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... Newton's next contribution to force theory was to unify the motions of heavenly bodies (which were assumed by Aristotle to be in a natural state of constant motion) with motion on the Earth. He proposed a law of gravity that could account for the celestial motions that had been described earlier using Kepler's Laws of Planetary Motion. His model for the force of gravity was so powerful that it was used successfully to predict the existence of massive bodies such as Neptune before they were actually observed. Gravitation is the tendency of masses to move toward each other. ... Johannes Keplers primary contributions to astronomy/astrophysics were his three laws of planetary motion. ... For other uses, see Neptune (disambiguation). ... In 1784 Charles Coulomb discovered the inverse square law of interaction between electric charges using a torsion balance, which was the second fundamental force. The weak and strong forces were discovered in the 20th century through the development of nuclear physics. 1784 was a leap year starting on Thursday (see link for calendar). ... Portrait of Coulomb Charles Augustin Coulomb (June 14, 1736—August 23, 1806) was a French physicist. ... Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... A torsion spring is a ribbon, bar, or coil that reacts against twisting motion. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... With the development of quantum field theory and general relativity it was realized that “force” is a redundant concept arising from conservation of momentum (4-momentum in relativity and momentum of virtual particles in QED). Thus currently known fundamental forces are more accurately called “fundamental interactions”. Quantum field theory (QFT) is the quantum theory of fields. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... In special relativity, four-momentum is a four-vector that replaces classical momentum; the four-momentum of a particle is defined as the particles mass times the particles four-velocity. ... In physics, a virtual particle is a particle which exists for such a short time and space that its energy and momentum do not have to obey the usual relationship. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... [edit] Describing forces Free-body diagrams of an object on a flat surface and an inclined plane. Forces are resolved and added together to determine their magnitudes and the resultant. Since forces can be directly perceived as a push or pull, this can provide an intuitive framework for describing forces. As with other physical concepts (e.g. temperature), the intuitive notion is quantified using operational definitions that are consistent with direct perception, but are more precise. Historically, forces were first quantitatively investigated in conditions of static equilibrium where several forces canceled each other out. Such experiments prove the crucial properties that forces are additive vector quantities: they have magnitude and direction. When two forces act on an object, the resulting force, the resultant, is the vector sum of the original forces. This is called the principle of superposition. The magnitude of the resultant varies from the difference of the magnitudes of the two forces to their sum, depending on the angle between their lines of action. As with all vector addition this results in a parallelogram rule: the addition of two vectors represented by sides of a parallelogram, gives an equivalent resultant vector which is equal in magnitude and direction to the transversal of the parallelogram. Image File history File links Freebodydiagram1. ... Image File history File links Freebodydiagram1. ... A free body diagram is a pictorial representation often used by physicists to show all contact and non-contact forces acting on the given free body. ... The inclined plane is one of the classical simple machines; as the name suggests, it is a flat surface whose endpoints are at different heights. ... For other uses, see Temperature (disambiguation). ... An operational definition of a quantity is the description of a specific process, or set of validation tests, accessible to more persons than the definer (i. ... In physics, static equilibrium, or neutral balance, exists when the forces (actions), and torques, on all components of a defined system are balanced such that no component is undergoing an acceleration relative to the designated frame of reference. ... This article is about vectors that have a particular relation to the spatial coordinates. ... The magnitude of a mathematical object is its size: a property by which it can be larger or smaller than other objects of the same kind; in technical terms, an ordering of the class of objects to which it belongs. ... The shape of each panel of this road sign, and the broken lines at the ends, represents an arrow; a space-consuming central bar of the arrow sign is dispensed with. ... A vector in physics and engineering typically refers to a quantity that has close relationship to the spatial coordinates, informally described as an object with a magnitude and a direction. The word vector is also now used for more general concepts (see also vector and generalizations below), but in this... In physics, the principle of superposition states that the net displacement at a given place and time caused by two or more waves traversing the same space is the vector sum of the displacements which would have been produced by the individual waves separately. ... In mathematics, the simplest form of the parallelogram law belongs to elementary geometry. ... Free-body diagrams can be used to provide a convenient way to keep track of forces acting on a system. Ideally, these diagrams are drawn with the angles and relative magnitudes of the force vectors preserved so that graphical vector addition can be done to determine the resultant. A free body diagram is a pictorial representation often used by physicists to show all contact and non-contact forces acting on the given free body. ... As well as being added, forces can also be resolved into independent components at right angles to each other. For example, a horizontal force pointing northeast can be split into two forces, one pointing north, and one pointing east. By the laws of vector addition, summing these component forces using vector addition yields the original force. Resolving force vectors into components of a set of basis vectors is often a more mathematically clean way to describe forces than using magnitudes and directions. This is because for orthogonal components, the components of the vector sum are uniquely determined by the scalar addition of the components of the individual vectors. In other words, orthogonal components are independent of each other: forces acting ninety degrees to each other have no effect on each other. Choosing a set of orthogonal basis vectors is often done by considering what set of basis vectors will make the mathematics most convenient. For example, in many cases choosing a basis vector that is directed in the direction of one of the forces is desirable since that force would then have only one non-zero component. Force vectors can also be three-dimensional, with the third component at right-angles to the two other components. This article is about angles in geometry. ... In mathematics, a subset B of a vector space V is said to be a basis of V if it satisfies one of the four equivalent conditions: B is both a set of linearly independent vectors and a generating set of V. B is a minimal generating set of V... In mathematics, orthogonal is synonymous with perpendicular when used as a simple adjective that is not part of any longer phrase with a standard definition. ... Equilibrium occurs when the resultant force acting on an object is zero (that is, the vector sum of all forces is zero). There are two kinds of equilibrium: static equilibrium and dynamic equilibrium. Look up equilibrium in Wiktionary, the free dictionary. ... In physics, static equilibrium, or neutral balance, exists when the forces (actions), and torques, on all components of a defined system are balanced such that no component is undergoing an acceleration relative to the designated frame of reference. ... A dynamic equilibrium occurs when two reversible processes occur at the same rate. ... [edit] Static equilibrium Static equilibrium was understood well before the invention of classical mechanics and states that objects which are at rest have a net zero resultant force acting on them. The simplest case of static equilibrium occurs when two forces are equal in magnitude but opposite in direction. For example, any object on a level surface is pulled (attracted) downward toward the center of the Earth by the force of gravity. At the same time, surface forces resist the downward force with equal upward force (called the normal force) and result in the object having a non-zero weight. The situation is one of zero net force and no acceleration. Fn represents the normal force. ... For other uses, see Weight (disambiguation). ... Pushing against an object on a frictional surface can result in a situation where the object does not move because the applied force is opposed by static friction, generated between the object and the table surface. For a situation with no movement, the static friction force exactly balances the applied force resulting in no acceleration. The static friction increases or decreases in response to the applied force up to an upper limit determined by the characteristics of the contact between the surface and the object. Determining the Coefficient of Friction. ... A static equilibrium between two forces is the most usual way of measuring forces, using simple devices such as weighing scales and spring balances. For example, an object suspended on a vertical spring scale experiences the force of gravity acting on the object balanced by a force applied by the "spring reaction force" which is equal to the object's weight. Using such tools, several quantitative force laws were discovered: that the force of gravity is proportional to volume for objects of constant density (widely exploited for millennia to define standard weights); Archimedes' principle for buoyancy; Archimedes' analysis of the lever; Boyle's law for gas pressure; and Hooke's law for springs. All these were all formulated and experimentally verified before Isaac Newton expounded his three laws of motion. Digital kitchen scales. ... Spring BAlance- it is a machine that measured the gravitational forces of earth which is Nine point eight Per second squared. ... Spring scale. ... For other uses, see Density (disambiguation). ... In physics, buoyancy is an upward force on an object immersed in a fluid (i. ... For other uses, see Archimedes (disambiguation). ... For the Portuguese town and parish, see Lever, Portugal. ... Boyles law (sometimes referred to as the Boyle-Mariotte law) is one of the gas laws and basis of derivation for the ideal gas law, which describes the relationship between the product pressure and volume within a closed system as constant when temperature remains at a fixed measure; both... Hookes law accurately models the physical properties of common mechanical springs for small changes in length. ... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Newtons First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ... [edit] Dynamical equilibrium Dynamical equilibrium was first described by Galileo who noticed that certain assumptions of Aristotlean physics were contradicted by observations and logic. Galileo realized that simple velocity addition demands that the concept of an "absolute rest frame" did not exist. Galileo concluded that motion in a constant velocity was completely equivalent to rest. This was contrary to Aristotle's notion of a "natural state" of rest that all massive objects naturally approached. Simple experiments showed that Galileo's understanding of the equivalence of constant velocity and rest to be correct. For example, if a mariner dropped a cannonball from the crow's nest of a ship moving at a constant velocity, Aristotlean physics would have the cannonball fall straight down while the ship moved underneath it. Thus, in an Aristotlean universe, the falling cannonball would land behind the foot of the mast of a moving ship. However, when this experiment is actually conducted, the cannonball always falls at the foot of the mast, as if the cannonball knows to travel with the ship despite being separated from it. Since there is no forward horizontal force being applied on the cannonball as it falls, the only conclusion left is that the cannonball continues to move with the same velocity as the boat as it falls. Thus, no force is required to keep the cannonball moving at the constant forward velocity. Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... For other uses, see Observation (disambiguation). ... Logic (from Classical Greek λόγος logos; meaning word, thought, idea, argument, account, reason, or principle) is the study of the principles and criteria of valid inference and demonstration. ... In general, the principle of relativity is the requirement that the laws of physics be the same for all observers. ... In special relativity the rest frame of a particle is the coordinate system (frame of reference) in which the particle is at rest. ... This article is about velocity in physics. ... Moreover, any object traveling at a constant velocity must be subject to a net zero resultant force. This is the definition of dynamical equilibrium where all the forces on an object balance but there is still constant velocity motion. A simple case of dynamical equilibrium occurs in constant velocity motion across a surface with kinetic friction. In such a situation, a force is applied in the direction of motion while the kinetic friction force exactly opposes the the applied force. This results in a net zero force, but since the object started with a non-zero velocity, it continues to move with a non-zero velocity. Aristotle misinterpreted this motion as being caused by the applied force. However, when kinetic friction is taken into consideration it is clear that there is no force causing constant velocity motion. Kinetic friction is the type of friction that an object is subject to after it is in motion. ... [edit] Newtonian definitions Though Sir Isaac Newton's most famous equation is F=ma, he actually wrote down a different form for his second law of motion that used differential calculus. In Principia Mathematica Newton set out three laws of motion which have direct relevance to the way forces are described in physics Godfrey Knellers portrait of Isaac Newton (1689) oil on canvas. ... Godfrey Knellers portrait of Isaac Newton (1689) oil on canvas. ... Sir Isaac Newton in Knellers portrait of 1689. ... Newtons first and second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ... Differential calculus is the theory of and computations with differentials; see also derivative and calculus. ... Newtons own copy of his Principia, with handwritten corrections for the second edition. ... [edit] Newton's first law Main article: Newton's first law Newton's first law of motion sets forth the conditions required for equilibrium and effectively defines the inertia that can be related to the mass of an object. Taking the Aristotlean idea of "natural states", the condition of constant velocity whether it be zero or nonzero is now considered the "natural state" of all massive objects. Objects will continue to move in a state of constant velocity unless acted upon by an unbalanced external force. Newtons laws of motion are three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ... This article is about inertia as it applies to local motion. ... [edit] Newton's second law Main article: Newton's second law Force is often defined using Newton's second law, as the product of mass m times acceleration : Newtons laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ... Newtons laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ... For other uses, see Mass (disambiguation). ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... Sometimes called the "second most famous formula in physics", Newton, in fact, never stated explicitly the F=ma formula for which he is often credited. Newton's second law is described in his Principia Mathematica as Newtons first and second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ... where is the momentum of the system. This article is about momentum in physics. ... The use of Newton's second law in either of these forms as a definition of force is generally disparaged in more rigorous textbooks,[1] because this removes all empirical content from the law. In fact, the in this equation represents the net (vector sum) force; in equilibrium this is zero by definition, but (balanced) forces are present nevertheless. Instead, Newton's law is meaningful because it asserts the proportionality of two quantities which can be defined without reference to it. Thus, the intuitive Aristotelian belief that a net force is required to keep an object moving with constant velocity (therefore zero acceleration) is objectively wrong and not just a consequence of a poor choice definition. With rather more justification, Newton's second law can be taken as a quantitative definition of mass by writing the law as an equality, the relative units of force and mass are fixed. Given the empirical success of Newton's law, it is sometimes used to measure the strength of forces (for instance, using astronomical orbits to determine gravitational forces). Nevertheless, the force and the quantities used to measure it remain distinct concepts. The definition of force is sometimes regarded as problematic, since it must either ultimately be referred to our intuitive understanding of our direct perceptions, or be defined implicitly through a set of self-consistent mathematical formulae. Notable physicists, philosophers and mathematicians who have sought a more explicit definition include Ernst Mach, Clifford Truesdell and Walter Noll.[2] Ernst Mach Ernst Mach (February 18, 1838 – February 19, 1916) was an Austrian-Czech physicist and philosopher and is the namesake for the Mach number and the optical illusion known as Mach bands. ... Clifford Ambrose Truesdell III, February 18, 1919 – January 14, 2000 was an American mathematician, physicist, fluid dynamicist, historian of mechanics, and polemicist. ... [edit] Newton's third law Main article: Newton's third law Newton's third law is a result of applying symmetry to situations where forces can be attributed to the presence of different objects. For any two objects (call them 1 and 2), Newton's third law states that Newtons laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. ... Sphere symmetry group o. ... This law implies that forces always occur in action-reaction pairs. Any force that is applied to object 1 due to the action of object 2 is automatically accompanied by a force applied to object 2 due to the action of object 1. If object 1 and object 2 are considered to be in the same system, then the net force on the system due to the interactions between objects 1 and 2 is zero since . This means that systems cannot create internal forces that are unbalanced. However, if objects 1 and 2 are considered to be in separate systems, then the two systems will each experience an unbalanced force and accelerate with respect to each other according to Newton's second law. Combining Newton's second and third laws, it is possible to show that the linear momentum of a system is conserved. Using In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... and integrating over time, the equation: Look up integration in Wiktionary, the free dictionary. ... is obtained. For a system which includes objects 1 and 2, which is the conservation of linear momentum. Generalizing this to a system of an arbitrary number of particles is straightforward. This shows that as a momentum between constituent objects will not affect the net momentum of a system. In general, as long as all forces are due to the interaction of massive objects, it is possible to define a system such that net momentum is never lost nor gained. [edit] Types of force Although there are apparently many types of forces in the Universe, they are all based on four fundamental forces. The strong and weak forces only act at very short distances and are responsible for holding certain nucleons and compound nuclei together. The electromagnetic force acts between electric charges and the gravitational force acts between masses. All other forces are based on the existence of the four fundamental interactions. For example, friction is a manifestation of the electromagnetic force acting between the atoms of two surfaces, and the Pauli exclusion principle, which does not allow atoms to pass through each other. The forces in springs modeled by Hooke's law are also the result of electromagnetic forces and the exclusion principle acting together to return the object to its equilibrium position. Centrifugal forces are acceleration forces which arise simply from the acceleration of rotating frames of reference. Nucleon is the common name used in nuclear chemistry to refer to a neutron or a proton, the components of an atoms nucleus. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... For other uses, see Mass (disambiguation). ... For other uses, see Friction (disambiguation). ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... Properties For other meanings of Atom, see Atom (disambiguation). ... An open surface with X-, Y-, and Z-contours shown. ... For other uses, see Spring. ... Hookes law accurately models the physical properties of common mechanical springs for small changes in length. ... Centrifugal force (from Latin centrum centre and fugere to flee) is a term which may refer to two different forces which are related to rotation. ... A frame of reference in physics is a set of axes which enable an observer to measure the aspect, position and motion of all points in a system relative to the reference frame. ... The modern quantum mechanical view of the first three fundamental forces (all except gravity) is that particles of matter (fermions) do not directly interact with each other but rather by exchange of virtual particles (bosons). This exchange results in what we call electromagnetic interaction (Coulomb force is one example of electromagnetic interaction). Fermions, named after Enrico Fermi, are particles which form totally-antisymmetric composite quantum states. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... Boson (game) Bosons, named after Satyendra Nath Bose, are particles which form totally-symmetric composite quantum states. ... Electromagnetic interaction is a fundamental force of nature and is felt by charged leptons and quarks. ... In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrical force that one stationary, electrically charged substance of small volume (ideally, a point source) exerts on another. ... It is a common misconception to ascribe the repulsion of like charges under the influence of the electromagnetic force to the stiffness and rigidity of solid matter. However, these characteristics are actually a result of the Pauli exclusion principle. Since electrons are fermions, they are forbidden by the rules of quantum mechanics from occupying the same quantum mechanical state as other electrons. This means that two electrons of the same quantum numbers cannot share the same atomic orbital, so when two electrons are brought in close proximity they simply cannot at any point occupy the volume of space already occupied by other electrons. The more densely compact the electrons in the material are, the more difficult it is to find allowable states for other electrons to inhabit. While this effect is manifested macroscopically as a structural "force", it is technically only the result of the existence of a finite ensemble of electron orbitals rather than being dependent directly on, for example, the electromagnetic force. All the electromagnetic force does is mediate the particular distribution and variety of the orbitals for the collection of atoms. Even if the electromagnetic force did not exist, fermions would still be excluded from occupying the same state. Such degeneracy pressure forces can only be overcome when there is enough energy in the system so that other fundamental interactions between the particles can take precedence (for example, electrons and protons interacting via the weak nuclear force to become neutrons). However, this kind of event only occurs in very extreme circumstances such as particle accelerators or neutron stars. Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925. ... For other uses, see Electron (disambiguation). ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... This article discusses the concept of a wavefunction as it relates to quantum mechanics. ... Quantum numbers describe values of conserved quantity in the dynamics of the quantum system. ... In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ... Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... For the DC Comics Superhero also called Atom Smasher, see Albert Rothstein. ... For the Hugo Award-winning story by Larry Niven, see Neutron Star (story). ... [edit] Gravity Main article: gravity What we now call gravity was not identified as a universal force until the work of Isaac Newton. Before Newton, the tendency for objects to fall towards the Earth was not understood as related to the motions of celestial objects. Galileo was instrumental in describing the characteristics of falling objects by determining that the acceleration of every body in free-fall was constant and independent of the mass of the object. Today, this acceleration due to gravity at the surface of the Earth is usually designated as and has a value of 9.81 meters per second squared which varies slightly depending on location and points toward the center of the Earth. This observation means that the force of gravity on an object at the Earth's surface is directly proportional to the object's mass. Thus an object that has a mass, m will experience a force Gravity is a force of attraction that acts between bodies that have mass. ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... Free Fall opens with one of the most stunning first paragraphs I have ever, or am ever likely to, read. ... For other uses, see Mass (disambiguation). ... The nominal acceleration due to gravity at sea level on the Earths surface, also known as standard gravity, is defined as exactly 9. ... The metre, or meter (symbol: m) is the SI base unit of length. ... This article is about the unit of time. ... In free-fall, this force is unopposed and therefore the net force on the object is the force of gravity. For objects not in free-fall, the force of gravity is opposed by the weight of the object. For example, a person standing on the ground experiences zero net force since the force of gravity is canceled by the weight of the person that is manifested by a normal force exerted on the person by the ground. For other uses, see Weight (disambiguation). ... Fn represents the normal force. ... Newton came to realize that the acceleration due to gravity at the surface of the Earth would manifest in different ways at larger distances. In particular, Newton determined that the acceleration of the moon around the Earth could be ascribed to the same force of gravity if the acceleration due to gravity decreased as an inverse square law. Further, Newton realized that the mass of the gravitating object directly affected the acceleration due to gravity. Combining these ideas gives a formula that relates the mass of the Earth (), the radius of the Earth () to the acceleration due to gravity: In physics, an inverse-square law is any physical law stating that some quantity is inversely proportional to the square of the distance from a point. ... where the vector direction is given by which is the unit vector in the direction of the center of the Earth. In mathematics, a unit vector in a normed vector space is a vector (often a spatial vector) whose length, (or magnitude) is 1. ... In this equation, a dimensional constant G is used to describe the relative strength of gravity. This constant has come to be known as Newton's Universal Gravitation Constant, though it was of an unknown value in Newton's lifetime. It was not until 1798 that Henry Cavendish was able to make the first measurement of the constant using a torsion balance which was widely reported in the press as a measurement of the mass of the Earth due to the fact that knowing the constant could allow one to solve for the Earth's mass given the above equation. Newton, however, realized that since all celestial bodies followed the same laws of motion, his law of gravity had to be universal. Succinctly stated, Newton's Law of Gravitation bewteen two massive bodies is According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ... For other persons named Henry Cavendish, see Henry Cavendish (disambiguation). ... A torsion spring is a ribbon, bar, or coil that reacts against twisting motion. ... Johannes Keplers primary contributions to astronomy/ astrophysics were the three laws of planetary motion. ... The law of universal gravitation states that gravitational force between masses decreases with the distance between them, according to an inverse-square law. ... where m1 is the mass of first object and m2 is the mass of the second object. This formula was powerful enough to stand as the basis for all subsequent descriptions of motion within the solar system until the twentieth century. During that time, sophisticated methods of perturbation analysis were invented to calculate the deviations of orbits due to the influence of multiple bodies on a planet, moon, comet, or asteroid. These techniques are so powerful that they can be used to predict precisely the motion of celestial bodies to an arbitrary precision at any length of time in the future. The formalism was exact enough to allow mathematicians to predict the existence of the planet Neptune before it was observed. Perturbation theory comprises mathematical methods that are used to find an approximate solution to a problem which cannot be solved exactly, by starting from the exact solution of a related problem. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article is about the astronomical term. ... This article is about Earths moon. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... For other uses, see Asteroid (disambiguation). ... For other uses, see Neptune (disambiguation). ... It was only in the orbit of the planet Mercury where Newton's Law of Gravitation seemed to not fully explain the orbit. Some astrophysicists predicted the existence of another planet (Vulcan) that would explain the discrepancies, but despite some early indications, no such planet could be found to exist. When Albert Einstein finally formulated his theory of general relativity (GR) he turned his attention to the problem of Mercury's orbit and found that his theory added a correction which could account for the discrepancy. This was the first instance where Newton's Theory of Gravity had been shown to be incorrect in favor of an alternative. [[Link titleBold text // ]] This article is about the planet. ... Vulcan was the name given to a small planet proposed to exist in an orbit between Mercury and the Sun in a 19th-century hypothesis. ... “Einstein” redirects here. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... Since then, general relativity has been acknowledged as the theory which currently explains gravity the best. In GR, interestingly gravitation is not viewed as a force, but rather, objects moving freely in gravitational fields travel under their own inertia in straight lines through curved space-time - defined as the shortest space-time path between two space-time events. From the perspective of the object, all motion occurs as if there were no gravitation whatsoever. It is only when observing the motion in a global sense that the curvature of spacetime can be observed and the force is inferred from the object's apparently curved path. Thus, the straight line path in space-time is seen as a curved line in space, and it is called the ballistic trajectory of the object. For example, a basketball thrown from the ground moves in a parabola shape as it is in a uniform gravitational field. Its space-time trajectory (when the extra ct dimension is added) is almost a straight line, slightly curved (with the radius of curvature of the order of few light-years). The time derivative of the changing momentum of the body is what we label as "gravitational force". In mathematics, a geodesic is a generalization of the notion of a straight line to curved spaces. In presence of a metric, geodesics are defined to be (locally) the shortest path between points on the space. ... In gravitational theory, gravity can deflect and modify the behaviour of light, causing spatial distances (measured by light) to be progressively modified or warped. ... External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. ... Mathematically the term trajectory refers to the ordered set of states which are assumed by a dynamical system over time (see e. ... This article is about the sport. ... A parabola A graph showing the reflective property, the directrix (light blue), and the lines connecting the focus and directrix to the parabola (blue) In mathematics, the parabola (from the Greek: παραβολή) (IPA pronunciation: ) is a conic section generated by the intersection of a right circular conical surface and a plane... The distance from the center of a sphere or ellipsoid to its surface is its radius. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ... [edit] Electromagnetic forces Main article: electromagnetism The electrostatic force was first described in 1784 by Coulomb as a force which existed intrinsically between two charges. The properties of the electrostatic force were that it varied as an inverse square law directed in the radial direction, was both attractive and repulsive (there was intrinsic polarity), was independent of the mass of the charged objects, and followed the law of superposition. Unifying all these observations into one succinct statement became known as Coulomb's Law. Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... In physics, the electrostatic force is the force arising between static (that is, non-moving) electric charges. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... In physics, an inverse-square law is any physical law stating that some quantity is inversely proportional to the square of the distance from a point. ... This article describes some of the common coordinate systems that appear in elementary mathematics. ... The polarity of an object is, in general, its physical alignment of atoms. ... See here for the superposition principle of physics. ... Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ... As the mathematical formalism for Coulomb's Law, physicists of the eighteenth and nineteenth century became interested in the electric field which could be used to determine the electrostatic force on an electric charge at any point in space. Knowing the magnitude of the electric field automatically gave the information required to know what the force applied on a given electric charge would be. In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Developing in parallel to electrostatic force was the Lorentz force of magnetism. This force can be described as a force that exists between two electric currents. It has the same mathematical character as Coulomb's Law with the proviso that like currents attract and unlike currents repel. Similar to the electric field, the magnetic field can be defined which can be used to determine the magnetic force on an electric current at any point in space. Combining the definition of electric current as the time rate of change of electric charge yields a law of vector multiplication called Lorentz's Law which determines the force on a moving charge provided with an electric field. Lorentz force. ... For other senses of this word, see magnetism (disambiguation). ... Electric current is the flow (movement) of electric charge. ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... Thus a full theory of the electromagnetic force on a charge can be written as a sum of the electrostatic force (due to the electric field) and the magnetic force (due to the magnetic field). Fully stated, this is the law: where is the magnitude of the electromagnetic force, q is the magnitude of the charge of the particle, is the velocity of the particle, is the electric field, and is the magnetic field. This article is about velocity in physics. ... The origin of electric and magnetic fields would not be fully explained until 1864 when James Clerk Maxwell finally unified a number of earlier theories into a succinct set of four equations that fully described the sources of the fields as due to stationary and moving charges as well as the interactions of the fields themselves. This led Maxwell to discover that electric and magnetic fields could be "self-generating" through a wave that traveled at a speed which he calculated to be the speed of light. This incredible insight united the nascent fields of electromagnetic theory with optics and led directly to a complete description of the electromagnetic spectrum. James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... Maxwells equations are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ... The wave equation is an important partial differential equation which generally describes all kinds of waves, such as sound waves, light waves and water waves. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ... For the book by Sir Isaac Newton, see Opticks. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... However, attempting to reconcile electromagnetic theory two observations, the photoelectric effect and the ultraviolet catastrophe, proved troublesome. Through the work of leading theoretical physicists, a new theory of electromagnetism was developed using quantum mechanics. This final modification to electromagnetic theory would lead ultimately to quantum electrodynamics which fully describes all electromagnetic phenomena as being mediated by waveparticles known as photons. In QED, photons are the fundamental exchange particle which described all interactions relating to electromagnetism including the electromagnetic force. A diagram illustrating the emission of electrons from a metal plate, requiring energy gained from an incoming photon to be more than the work function of the material. ... The ultraviolet catastrophe, also called the Rayleigh-Jeans catastrophe, was a prediction of early 20th century classical physics that an ideal black body at thermal equilibrium will emit radiation with infinite power. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... [edit] Nuclear forces Main article: nuclear force This article is about the force sometimes called the residual strong force. ... [edit] Force and potential Instead of a force, the mathematically equivalent concept of a potential energy field can be used for convenience. For instance, the gravitational force acting upon a body can be seen as the action of the gravitational field that is present at the body's location. Restating mathematically the definition of energy (via definition of work), a potential scalar field is defined as that field whose gradient is equal and opposite to the force produced at every point: Potential energy can be thought of as energy stored within a