
Inertia is the tendency of any state of affairs to persist in the absence of external influences. Specifically, in physics, it is ''the tendency of a body to maintain its state of uniform motion unless acted on by an external force''. (This is called Newton's ''Newton's laws of motion of motion'', taken from ''Galileo's principle''.) The term is also used in psychology to describe a person's resistance to change. ==History== The concept of ''inertia'' is alien to the physics of Aristotle which provided the standard account of motion until the 17th century. Aristotle, and his peripatetic followers, held that a body was only maintained in motion by the action of a continuous external force. Thus, in the Aristotelian view, a projectile moving through the air would owe its continuing motion to ''eddies'' or ''vibrations'' in the surrounding medium, a phenomenon known as ''antiperistasis''. In the absence of a proximate force, the body would come to rest immediately. In the 6th century, Joannes Philoponus first criticised Aristotle's notion and proposed that motion was maintained by some property of the body, imparted when it was set in motion. This view was strongly opposed by Averroës and the scholastic philosophers who supported Aristotle. William of Occam argued forcibly for Philoponus's theory but supporters still held the view that the property which maintained the motion also dissipated as it moved. In the 14th century, Jean Buridan named the motion-maintaining property ''impetus'' and rejected the view that it dissipated spontaneously, asserting that a body would be arrested by the forces of air resistance and gravity which might be opposing its impetus. Buridan further held that the impetus of a body increased with the speed with which it was set in motion, and with its quantity of matter. Clearly, Buridan's impetus is closely related to the modern concept of momentum. Buridan anticipated Isaac Newton when he wrote: :''...after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion'' Buridan used the theory of impetus to give an accurate qualitative account of the motion of projectiles but he ultimately saw his theory as a correction to Aristotle, maintaining core peripatetic beliefs including a fundamental qualitative difference between motion and rest. The theory of impetus was adapted to explain celestial mechanics phenomena in terms of ''circular impetus''. Leonardo da Vinci, mistakenly, wrote ''Everything moveable thrown with fury through the air continues the motion of its mover; if, therefore, the latter move in a circle and release it in the course of this motion, its movement will be curved.'' Sometime between 1589 and 1592, Galileo Galilei started researching the motion of moving bodies using the impetus theory of Hipparchus. Following an audacious series of experiments, both in practice and in thought, Galileo came to reject the Aristotelian view and to formulate a new ''principle of inertia'', sometimes known as ''Galileo's principle'': :''Every object persists in its state of rest, or uniform motion (in a straight line); unless, it is compelled to change that state, by forces impressed on it.'' ==Newtonian mechanics== Newton adopted ''Galileo's principle'' as his Newton's laws of motion#Newton's First Law : Law of Inertia and set it within the wider context of what came to be known as Newtonian mechanics. In Newton's theory, no force is required to maintain a body in uniform motion, in contrast to Aristotle's view, where no force is needed to maintain a body at rest. The ''impetus'' of a body was the cause of motion but its Newtonian physics equivalent, ''momentum'' is simply descriptive, no cause being required. The loss of the ontology distinction between rest and motion leads to the concept of inertial frames which demand that observers in uniform (non-accelerating) motion all observe the same laws of physics. Observers in distinct inertial frames can make a very simple, and intuitively obvious, transformation (the Galilean transformation, a linear, sliding translation at constant velocity) to convert their observations for another's observations. Thus, an observer on a moving train sees a dropped ball fall vertically downwards, as does an observer of a similar ball in a stationary frame. The relationship holds because, on the train, which is moving at a constant velocity, the ball also has an inertia in the direction of travel that maintains its relative position, with respect to the moving train, when the ball is dropped. However, in non-inertial frames, ''accelerating observers'' encounter all sorts of ''fictitious forces'', such as the Coriolis effect, that would not be experienced in an inertial frame of reference (such as the frame of the "fixed stars" like Polaris). In summary, the principle of inertia is intimately linked with the principles of conservation of energy and conservation of momentum. Thus a change in momentum or energy would have to be applied to the observer or to the system in a conversion of the viewpoint from an inertial frame to some non-inertial frame. == Measuring Inertia == The Physical unit for inertia is the same as for mass. Typically it is expressed in grams or kilograms. The equivalence of mass and inertia seems to hold true according to all empirical evidence (see gravitational physics and also ''Mach's principle'', below). In theory at least they are sometimes regarded as being separate qualities. ==''Mach's principle''== Mach's principle deals with the question of the origin of inertia. Therefore it deals only with accelerated motion, not with uniform motion. Mach had stated that the absolute space that is assumed in newtonian dynamics is unsatisfactory in a philosophy of physics that demands that all dynamics is to be explained in terms of interactions of material objects. If there is absolute space then in a universe with just a single object in it that object will have inertia. A mass of water will contract itself to a sphere of water, and if this mass of water is spinning then it wil not be spherical in shape, but the shape will be an ellipsoid, due to inertia. In order to formulate a theory in which there is no necessity of assuming absolute space, it would have to be a theory in which the existence of inertia is due to an interaction of local matter with distant matter, a theory in which the existence of inertia is due to interaction of local matter with all of the matter in the universe. Albert Einstein named this ''Mach's principle''. In Newton's judgement, assuming absolute space was an unavoidable necessity. The alternative would be to assume an action at a distance from the stars, and Newton was committed to avoiding assumptions of action-at-a-distance whenever possible. Newton needed absolute space for accelerated motion only; only with absolute space would water rotating in a bucket "know" what concave shape to take. However, for uniform motion newtonian dynamics implies that in all inertial reference frames the same laws of motion apply: the principle of Galilean relativity. Special relativity was a reassertion of this type of relativity: in all inertial reference frames the same laws of physics hold. In general relativity the description of gravity and the description of inertia are unified. Both are described as interaction of matter with the geometry of space-time. A force opposing gravity is described as the same physics as a force that is accelerating an object: both are described as an interaction with a gravito-inertial field. The gravito-inertial field exists because the universe exists. In general relativity the action at a distance is mediated by space-time geometry. Mach's original thought was to eliminate space altogether as a agent in physics. Newtonian absolute space acts on matter but is not acted upon by matter, that was very unsatisfactory. Einstein did the opposite of what Mach had envisioned, in general relativity space-time geometry is described as part of the realm of physical things. In general relativity space-time acts upon matter and it is acted upon by matter. =="Inertia" in non-mechanical systems== In mathematical descriptions of mechanical systems, the mass of a body appears in a term featuring the acceleration, the second derivative of displacement; as, for example, in the harmonic oscillator. It is this term that provides the ''dynamics'' of the system in that, if we vary the system slowly enough we can make the term small and the system behaves ''quasi-statically''. It is the interaction between the inertial term (involving the second derivative of displacement) and some ''restoring force'' (involving the zeroth derivative of displacement) that allows a system to oscillation. There are other physical phenomenon which exhibit similar behaviour and which are also described by second-order differential equations. *In these systems, the multiplier of the second derivative term plays a role analogous to ''mass'' in a mechanical system: in particular, ''inductance'' in loaded electrical systems and ''inertance'' in acoustical systems. *Importantly, there is no thermal analogue of inertia entailing that ''there are no un-driven thermal oscillations''. ==Rotational inertia== A further analogy is that of ''rotational inertia'' in which a rotating body maintains its state of uniform rotational motion. Thus its angular momentum would be unchanged, unless an external torque were to be applied. Rotational inertia often has hidden practical consequences. In the braking of a railway, arresting the linear motion would require that the substantial rotational inertia of the motors must be converted to some other forms of energy, thus causing acoustics vibration of the wheels and frictional heating of the brakes on the railway carriage. ==Intuitive physics== Commonly, when people unschooled in Newtonian physics are asked to make predictions about certain sorts of motions involving inertia, their responses are more likely to reflect the theories of Aristotle than of Newton. For example, they often do not realize that the hammer or steel ball in the hammer throw continues in a straight line. ==See also== Energy | General relativity | Inertial frame | Inertial guidance system | Inertial mass | Mach's principle | Momentum | Newton's laws of motion | Newtonian physics | Special relativity ==External links== *[http://www.seop.leeds.ac.uk/entries/buridan/ ''Jean Buridan'' Stanford Encyclopaedia of Philosophy] ==Books and papers== *Butterfield, H (1957) ''The Origins of Modern Science'' ISBN 071350160X *Clement, J (1982) "Students' preconceptions in introductory mechanics", ''American Journal of Physics'' vol 50, pp66-71 *Crombie, A C (1959) ''Medieval and Early Modern Science'', vol 2 *McCloskey, M (1983) "Intuitive physics", ''Scientific American'', April, pp114-123 *McCloskey, M & Carmazza, A (1980) "Curvilinear motion in the absence of external forces: naïve beliefs about the motion of objects", ''Science'' vol 210, pp1139-1141 Classical mechanics Introductory physics lv:Inerce
http://arxiv.org/abs/physics/0211106 UNIVERSALITY Emil Marinchev, Technical University of Sofia, Physics Department, 8 Kliment Ohridski St., Sofia-1000, BG, e-mail: emar@tu-sofia.bg Abstract: This article is an attempt for a new vision of the basics of Physics, and of Relativity, in particular. A new generalized principle of inertia is proposed, as an universal principle, based on universality of the conservation laws, not depending on the metric geometry used. The second and the third principles of Newton's mechanics are interpreted as logical consequences. The generalization of the classical principle of relativity made by Einstein as the most basic postulate in the Relativity is criticized as logically not well-founded. A new theoretical scheme is proposed based on two basic principles: 1.The principle of universality of the conservation laws, and 2.The principle of the universal velocity. It is well- founded with examples of different fields of physics. Comments: 5 pages, 1 figure, Subj-class: General Physics, Key words:Universality, New Insight in Physics http://arxiv.org/abs/physics/0211106
See other meanings of words starting from letter:
Words begining with Inertia:
Inertia
Inertia
Inertial
Inertial-Centrifugal_propulsion
Inertial_Compensator
Inertial_compensator
Inertial_confinement_fusion
Inertial_damper
Inertial_electrostatic_confinement
Inertial_flow_meter
Inertial_force
Inertial_frame
Inertial_frames
Inertial_frames_of_reference
Inertial_frame_of_reference
Inertial_frame_of_reference
Inertial_fusion_energy
Inertial_guidance
Inertial_guidance_system
Inertial_guidance_system
Inertial_mass
Inertial_Measurement_Unit
Inertial_navigation
Inertial_navigation_system
Inertial_platform
Inertial_propulsion_engine
Inertial_propulsion_engine
Inertial_reference_frame
Inertial_reference_frame
Inertial_reference_frames
Inertial_tracking_device
Inertiam
Inertia_(comics)
Inertia_(DC_Comics)
Inertia_group
Inertia
Inertia is the tendency of any state of affairs to persist in the absence of external influences. Specifically, in physics, it is ''the tendency of a body to maintain its state of uniform motion unless acted on by an external force''. (This is called Newton's ''Newton's laws of motion of motion'', taken from ''Galileo's principle''.) The term is also used in psychology to describe a person's resistance to change. ==History== The concept of ''inertia'' is alien to the physics of Aristotle which provided the standard account of motion until the 17th century. Aristotle, and his peripatetic followers, held that a body was only maintained in motion by the action of a continuous external force. Thus, in the Aristotelian view, a projectile moving through the air would owe its continuing motion to ''eddies'' or ''vibrations'' in the surrounding medium, a phenomenon known as ''antiperistasis''. In the absence of a proximate force, the body would come to rest immediately. In the 6th century, Joannes Philoponus first criticised Aristotle's notion and proposed that motion was maintained by some property of the body, imparted when it was set in motion. This view was strongly opposed by Averroës and the scholastic philosophers who supported Aristotle. William of Occam argued forcibly for Philoponus's theory but supporters still held the view that the property which maintained the motion also dissipated as it moved. In the 14th century, Jean Buridan named the motion-maintaining property ''impetus'' and rejected the view that it dissipated spontaneously, asserting that a body would be arrested by the forces of air resistance and gravity which might be opposing its impetus. Buridan further held that the impetus of a body increased with the speed with which it was set in motion, and with its quantity of matter. Clearly, Buridan's impetus is closely related to the modern concept of momentum. Buridan anticipated Isaac Newton when he wrote: :''...after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion'' Buridan used the theory of impetus to give an accurate qualitative account of the motion of projectiles but he ultimately saw his theory as a correction to Aristotle, maintaining core peripatetic beliefs including a fundamental qualitative difference between motion and rest. The theory of impetus was adapted to explain celestial mechanics phenomena in terms of ''circular impetus''. Leonardo da Vinci, mistakenly, wrote ''Everything moveable thrown with fury through the air continues the motion of its mover; if, therefore, the latter move in a circle and release it in the course of this motion, its movement will be curved.'' Sometime between 1589 and 1592, Galileo Galilei started researching the motion of moving bodies using the impetus theory of Hipparchus. Following an audacious series of experiments, both in practice and in thought, Galileo came to reject the Aristotelian view and to formulate a new ''principle of inertia'', sometimes known as ''Galileo's principle'': :''Every object persists in its state of rest, or uniform motion (in a straight line); unless, it is compelled to change that state, by forces impressed on it.'' ==Newtonian mechanics== Newton adopted ''Galileo's principle'' as his Newton's laws of motion#Newton's First Law : Law of Inertia and set it within the wider context of what came to be known as Newtonian mechanics. In Newton's theory, no force is required to maintain a body in uniform motion, in contrast to Aristotle's view, where no force is needed to maintain a body at rest. The ''impetus'' of a body was the cause of motion but its Newtonian physics equivalent, ''momentum'' is simply descriptive, no cause being required. The loss of the ontology distinction between rest and motion leads to the concept of inertial frames which demand that observers in uniform (non-accelerating) motion all observe the same laws of physics. Observers in distinct inertial frames can make a very simple, and intuitively obvious, transformation (the Galilean transformation, a linear, sliding translation at constant velocity) to convert their observations for another's observations. Thus, an observer on a moving train sees a dropped ball fall vertically downwards, as does an observer of a similar ball in a stationary frame. The relationship holds because, on the train, which is moving at a constant velocity, the ball also has an inertia in the direction of travel that maintains its relative position, with respect to the moving train, when the ball is dropped. However, in non-inertial frames, ''accelerating observers'' encounter all sorts of ''fictitious forces'', such as the Coriolis effect, that would not be experienced in an inertial frame of reference (such as the frame of the "fixed stars" like Polaris). In summary, the principle of inertia is intimately linked with the principles of conservation of energy and conservation of momentum. Thus a change in momentum or energy would have to be applied to the observer or to the system in a conversion of the viewpoint from an inertial frame to some non-inertial frame. == Measuring Inertia == The Physical unit for inertia is the same as for mass. Typically it is expressed in grams or kilograms. The equivalence of mass and inertia seems to hold true according to all empirical evidence (see gravitational physics and also ''Mach's principle'', below). In theory at least they are sometimes regarded as being separate qualities. ==''Mach's principle''== Mach's principle deals with the question of the origin of inertia. Therefore it deals only with accelerated motion, not with uniform motion. Mach had stated that the absolute space that is assumed in newtonian dynamics is unsatisfactory in a philosophy of physics that demands that all dynamics is to be explained in terms of interactions of material objects. If there is absolute space then in a universe with just a single object in it that object will have inertia. A mass of water will contract itself to a sphere of water, and if this mass of water is spinning then it wil not be spherical in shape, but the shape will be an ellipsoid, due to inertia. In order to formulate a theory in which there is no necessity of assuming absolute space, it would have to be a theory in which the existence of inertia is due to an interaction of local matter with distant matter, a theory in which the existence of inertia is due to interaction of local matter with all of the matter in the universe. Albert Einstein named this ''Mach's principle''. In Newton's judgement, assuming absolute space was an unavoidable necessity. The alternative would be to assume an action at a distance from the stars, and Newton was committed to avoiding assumptions of action-at-a-distance whenever possible. Newton needed absolute space for accelerated motion only; only with absolute space would water rotating in a bucket "know" what concave shape to take. However, for uniform motion newtonian dynamics implies that in all inertial reference frames the same laws of motion apply: the principle of Galilean relativity. Special relativity was a reassertion of this type of relativity: in all inertial reference frames the same laws of physics hold. In general relativity the description of gravity and the description of inertia are unified. Both are described as interaction of matter with the geometry of space-time. A force opposing gravity is described as the same physics as a force that is accelerating an object: both are described as an interaction with a gravito-inertial field. The gravito-inertial field exists because the universe exists. In general relativity the action at a distance is mediated by space-time geometry. Mach's original thought was to eliminate space altogether as a agent in physics. Newtonian absolute space acts on matter but is not acted upon by matter, that was very unsatisfactory. Einstein did the opposite of what Mach had envisioned, in general relativity space-time geometry is described as part of the realm of physical things. In general relativity space-time acts upon matter and it is acted upon by matter. =="Inertia" in non-mechanical systems== In mathematical descriptions of mechanical systems, the mass of a body appears in a term featuring the acceleration, the second derivative of displacement; as, for example, in the harmonic oscillator. It is this term that provides the ''dynamics'' of the system in that, if we vary the system slowly enough we can make the term small and the system behaves ''quasi-statically''. It is the interaction between the inertial term (involving the second derivative of displacement) and some ''restoring force'' (involving the zeroth derivative of displacement) that allows a system to oscillation. There are other physical phenomenon which exhibit similar behaviour and which are also described by second-order differential equations. *In these systems, the multiplier of the second derivative term plays a role analogous to ''mass'' in a mechanical system: in particular, ''inductance'' in loaded electrical systems and ''inertance'' in acoustical systems. *Importantly, there is no thermal analogue of inertia entailing that ''there are no un-driven thermal oscillations''. ==Rotational inertia== A further analogy is that of ''rotational inertia'' in which a rotating body maintains its state of uniform rotational motion. Thus its angular momentum would be unchanged, unless an external torque were to be applied. Rotational inertia often has hidden practical consequences. In the braking of a railway, arresting the linear motion would require that the substantial rotational inertia of the motors must be converted to some other forms of energy, thus causing acoustics vibration of the wheels and frictional heating of the brakes on the railway carriage. ==Intuitive physics== Commonly, when people unschooled in Newtonian physics are asked to make predictions about certain sorts of motions involving inertia, their responses are more likely to reflect the theories of Aristotle than of Newton. For example, they often do not realize that the hammer or steel ball in the hammer throw continues in a straight line. ==See also== Energy | General relativity | Inertial frame | Inertial guidance system | Inertial mass | Mach's principle | Momentum | Newton's laws of motion | Newtonian physics | Special relativity ==External links== *[http://www.seop.leeds.ac.uk/entries/buridan/ ''Jean Buridan'' Stanford Encyclopaedia of Philosophy] ==Books and papers== *Butterfield, H (1957) ''The Origins of Modern Science'' ISBN 071350160X *Clement, J (1982) "Students' preconceptions in introductory mechanics", ''American Journal of Physics'' vol 50, pp66-71 *Crombie, A C (1959) ''Medieval and Early Modern Science'', vol 2 *McCloskey, M (1983) "Intuitive physics", ''Scientific American'', April, pp114-123 *McCloskey, M & Carmazza, A (1980) "Curvilinear motion in the absence of external forces: naïve beliefs about the motion of objects", ''Science'' vol 210, pp1139-1141 Classical mechanics Introductory physics lv:Inerce
Inertia
http://arxiv.org/abs/physics/0211106 UNIVERSALITY Emil Marinchev, Technical University of Sofia, Physics Department, 8 Kliment Ohridski St., Sofia-1000, BG, e-mail: emar@tu-sofia.bg Abstract: This article is an attempt for a new vision of the basics of Physics, and of Relativity, in particular. A new generalized principle of inertia is proposed, as an universal principle, based on universality of the conservation laws, not depending on the metric geometry used. The second and the third principles of Newton's mechanics are interpreted as logical consequences. The generalization of the classical principle of relativity made by Einstein as the most basic postulate in the Relativity is criticized as logically not well-founded. A new theoretical scheme is proposed based on two basic principles: 1.The principle of universality of the conservation laws, and 2.The principle of the universal velocity. It is well- founded with examples of different fields of physics. Comments: 5 pages, 1 figure, Subj-class: General Physics, Key words:Universality, New Insight in Physics http://arxiv.org/abs/physics/0211106
See other meanings of words starting from letter:
I
IA | IB | IC | ID | IE | IF | IG | IH | IJ | IK | IL | IM | IN | IO | IP | IR | IS | IT | IU | IW | IX | IY | IZ |Words begining with Inertia:
Inertia
Inertia
Inertial
Inertial-Centrifugal_propulsion
Inertial_Compensator
Inertial_compensator
Inertial_confinement_fusion
Inertial_damper
Inertial_electrostatic_confinement
Inertial_flow_meter
Inertial_force
Inertial_frame
Inertial_frames
Inertial_frames_of_reference
Inertial_frame_of_reference
Inertial_frame_of_reference
Inertial_fusion_energy
Inertial_guidance
Inertial_guidance_system
Inertial_guidance_system
Inertial_mass
Inertial_Measurement_Unit
Inertial_navigation
Inertial_navigation_system
Inertial_platform
Inertial_propulsion_engine
Inertial_propulsion_engine
Inertial_reference_frame
Inertial_reference_frame
Inertial_reference_frames
Inertial_tracking_device
Inertiam
Inertia_(comics)
Inertia_(DC_Comics)
Inertia_group
These materials are based on Wikipedia and licensed under the GNU FDL
YouTube.com videos better site than Turbo Tax 2007
