The object remains stationary orUniform linear motionThe nature of the state is called inertia.Inertia is an inherent attribute of an object, which is expressed as an impedance degree of the object to its movement state changes. Mass is a measure of the inertia of an object[1]。When the external force acting on the object is zero, the inertial performance is that the object keeps its motion state unchanged, that is, remains stationary or moves at a constant speed in a straight line;When the external force acting on the object is not zero, inertia is expressed as the difficulty of the external force changing the motion state of the object.Under the action of external force, the greater the mass of the object with the same acceleration, the greater the inertia.Therefore, the inertia of the object will not change or disappear at any time (under the action of external force or not) and under any circumstances (static or moving).Inertia is an attribute of matter itself.
In physics,inertia(inertia) is the property that an object resists the change of its motion state.The inertia of an object can be measured by its mass. The greater the mass, the greater the inertia.Isaac NewtonIn a great book《Mathematical Principles of Natural Philosophy》Inertia is defined as:
Inertia is an inherent property of matter and a phenomenon of resistance. It exists in every object, its size is proportional to the mass of the object, and it should try to keep it in its existing state, whether it is static orUniform linear motionstate。
More specifically,Newton's first lawIt shows that there are some reference systems in which the objects not subject to external forces remain stationary or move at a uniform speed in a straight line.In other words, from some reference systems, if the external force applied to the object is zero, the size and direction of the object's motion speed will be constant.Inertia is defined as that the object in Newton's first law has the property of maintaining the original state of motion.The reference system satisfying Newton's first law is calledInertial reference frame。A more detailed discussion of inertial reference systems will follow later.
Principle of inertiayesclassical mechanicsThe basic principle of.Many scholars believe that the principle of inertia is Newton's first law.Following this principle, an object will continue to move at its current speed unless an external force forces it to change its speed.
On the surface of the earth, inertia is oftenfriction、air resistanceAnd so on, which makes the moving speed of the object become slower and slower (usually it will finally become static).This phenomenon misled many ancient scholars, for example,AristotleIt is believed that in the universe, all objects have their "natural position" - in a perfect position, objects will be fixed in theirNatural location, the object will move only when an external force is applied.
definition
Inertia is an inherent property of all objects, whether solid, liquid or gas, whether the object is moving orstaticAll have inertia.All objects have inertia.
Inertia definition: we keep objectsmotion state The invariable property is called inertia.Inertia represents the difficulty of changing the motion state of an object.The magnitude of inertia is only related to the mass of the object.It is relatively difficult to change the motion state of objects with large mass, that is, the inertia is large;The motion state of objects with small mass is relatively easy to change, that is, the inertia is small.
When you kick the ball, it starts to move. At this time, because the ball has inertia, it will keep rolling until it is stopped by external force.Any object has inertia at any time, and it should maintain its original state of motion.[2]
be careful
inertia
1. Inertia is not equal to the law of inertia.Inertia is the nature of the object itself, and the law of inertia talks about the relationship between motion and force (force is not the reason for maintaining the motion of the object, but the reason for changing the motion state of the object).
2. Inertia is an inherent attribute of an object, and it cannot be said that "it is affected by inertia" or "it is obtained by inertia".The correct one is "inertia".[3]
history
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Early doctrine
Before the Renaissance, the most widely accepted theory of movement in western philosophy was established from about 335 BC to 322 BCAristotleThe theory of.Aristotle showed that if there is no "violent force", all objects (on the earth) will eventually stop moving and rest in their natural positions. However, as long as there is violence to promote the movement of objects, objects will continue to move.WhenThrowing objectsWhen being thrown out, the force of the thrower transfers to the air around the throwing object, making the air flow, becoming a new promoter, and continuously promoting the movement of the throwing object.
In the next two thousand years or so, Aristotle's concept of movement was widely accepted, and only a few famous philosophers questioned it.For example, in the sixth century,John Philoponos Criticize Aristotle's inconsistent theory of object movement: Aristotle believes thatvacuumIt is impossible to exist, because in vacuum, there is no medium to make the object move, but he also said that the resistance of the medium is proportional to its density: if the density of air is half of that of water, then the time spent by the object through the same path in air is half of that in water, then the time spent by the object through vacuum should be less.
Filaubonos argues that the medium can only hinder the movement of the projectile, and cannot promote the movement of the projectile;In vacuum, there is no medium, and the projectile is easier to move.Filaubonos suggested that the factors contributing to the continuous motion of the projectile have nothing to do with the surrounding medium, but rather a certain property imposed on the projectile at the beginning of the motion, which gradually dissipates during the motion.Although this proposal is still different from the current concept of inertia, at least it has stepped out of the basic step in the right direction.
However, during that period and many years after that, his ideas were not taken seriously, and many Aristotelian scholars strongly opposed them, includingThomas Acquinas (circa 1225-1274) andAlbertus Magnus(about 1200-1280).onlyWilliam of Occam (circa 1288-1348) ObjectionAristotelian Physics。He questioned where was the "promoter" of the movement mentioned by Aristotle?Although he denied the correctness of Aristotle's axiom, he believed that the motion of a projectile did not need to be accompanied by a promoter at any time and anywhere.However, he could not give any alternative answers.
character
1. Jean Bridan
In the 14th century, French philosophersjean buridan proposeImpulse theory。He calls the nature that causes objects to move asmomentumThe impulse is transmitted to the object by the driver to make the object move.He rejected the idea that momentum would run out.Bridan believes that the immortal impulse is gradually offset by air resistance or friction, as long as the impulse is greater than the resistance or friction[11]Wait, the object will continue to move.Bridan's impulse is proportional to the density and volume of the object;The greater the speed, the greater the impulse;The more matter inside an object, the more impulse it can accept.
Although very similar to the modern concept of inertia, Bridan only regarded his theory as a minor revision of Aristotle's basic philosophy, and insisted on many other Aristotelian ideas, for example, he believed that the state of motion and the state of rest were two different states.Bridan also claimed that impulse is not only applicable to linear motion, but also to circular motion, which makes objects (such as stars) move in a circle.
Albert of Saxony He is a student of Bridan.He spread Bridan's theory to Italy and Central Europe.stayMerton College, Oxford UniversityThinker ofWilliam of HertsburyFirst expressedAverage rate theorem: In the same time interval, if the speed of an object with constant speed is half of the sum of the initial speed and the final speed of an object with constant acceleration, then the two objects move at the same distance.This theorem isLaw of free fallThe foundation of.As early asGalileo Galilei They have already done experiments to prove this theorem.
2. Nick Orisim
Nicole Orisim gave full play to their research results, and he created a method to explain the law of motion with curve graphs, and proved the average speed theorem with geometric methods.Orisim's work published in 1377《General Theory of Heaven and Earth》It is pointed out that when the free falling body accelerates, its weight does not increase, but its impulse increases.Suppose that a straight tunnel is excavated from point A on the earth's surface, through the geocenter, to point B on the earth's surface, and then a heavy object falls into the tunnel, then it will move from point A, through the geocenter, to point B, as if a pendulum swings from one side to the other.However, on the way from the center of the earth to point B, it is in a rising state, and the weight can only cause objects to fall, so the impact is different from the weight.
3. Nicolas Copernicus
Nicolaus Copernicus Published in 1543《Celestial motion theory》, claiming that the earth (and all objects on its surface) never stops moving, but continues to revolve around the sun.In the face of this new theory, AristotelianGeocentric theory——The earth is the center of the universe, so it is absolutely fixed - it seems to be full of holes and difficult to parry.Before he published his work, Copernicus had already completed the experiment of observing the orbital motion of planets in 1530 in order to verify his theory.
4. Kepler
German astronomerKeplerThe term "inertia" was first put forward in the book "Copernican Astronomical Outline" published in three stages from 1618 to 1621, which means "laziness" in Latin, which is different from today's interpretation.Kepler defined inertia as resistance to motion changes, which is still the premise of taking Aristotle's static state as the natural state.It was not until Galileo's research and Newton's unification of stillness and motion in the same principle that the term inertia could be applied to the concept it has today.
according toAristotleIn the physics of physics, what keeps objects moving at a uniform speed is the lasting effect of force.But Galileo's experiment proved that the objectgravitationUnder the lasting influence ofUniform motionOn the contrary, the speed increases after a certain time.The object continues to maintain its speed at any point and is intensified by gravity.If gravity can be cut off, the object will continue to move at the speed it obtained at that point.Galileo observed in the experiment of metal ball rolling on an inclined plane that the metal ball continued to roll over a smooth flat table at a uniform speed.From these observations, the principle of inertia is obtained.This principle explains that as long as an object is not affected by external forces, it will keep its original static state or uniform motion state unchanged.
He argued that it was the speed, not the position, of the object that was changed by the external force;No external force is required to maintain the speed of the object.In order to prove his claim, Galileo did an ideological experiment.Let the stationary ball roll down from point AInclined planeAB，After rolling to the bottom, the ball will roll up the slope BC. Assuming that both slopes are very smooth, the friction coefficient is very small, and the air resistance is so weak that it can be ignored, the ball will roll to point C at the same height as point A;Assuming that the slope is BD, BE or BF, the ball will also roll to the same height as point A.However, the longer the slope, the smaller the decrease in speed per unit time when rolling upward.Assuming that the slope gradually lengthens and finally becomes the horizontal BH, then“Principle of continuity”The ball "should have" returned to the same height as point A. However, because BH is horizontal in fact, the ball can never roll to the previous height, and the decrease in speed will become 0, so the ball will keep showingUniform linear motion。Galileo concluded that if there is no obstacle, the moving object will continue to move in a uniform straight line.He called thisLaw of inertia。
When this theory was first proposed, it was not accepted by other scholars because most scholars did not understand the essence of friction and air resistance at that time. However, Galileo's experiment was based on reliable facts. Through abstract thinking, he grasped the main factors and ignored the secondary factors, which more profoundly reflected the laws of nature.
It is worth noting that later, Galileo deduced from the law of inertia that if there is no external reference comparison, it is absolutely impossible to distinguish whether an object is stationary or moving.This observation later became the basis for Einstein's development of his special theory of relativity.
Galileo's principle of inertia is the starting point of modern science, which destroyed oppositionCopernicusThe so-called lack of direct evidence of the earth movement excuse.
6. Descartes
Descartes and others are here againGalileoOn the basis of the research, he carried out more in-depth research. He believed that if the moving object is not affected by any force, not only the speed will not change, but also the direction of motion will not change, and it will move along the original direction at a uniform speed[2]
7. Newton
The principle of inertia commonly recognized in modern society comes from Newton's《Mathematical Principles of Natural Philosophy》(Mathematical Principles of Natural Philosophy, 1687), defined as follows:
The law of inertia isNewton's first law。
All objects will always be at rest or in uniform linear motionstateUntil the force applied on it changes its motion state.
After writing Newton's first law, Newton began to describe the natural motion of various objects he observed.Like flying arrows and rocksProjectileIf they are not resisted by the resistance of air or attracted by gravity, they will continue to move at a constant speed.imagetopA kind of rotating body, if it is not affected by the groundfrictionLoss, they will rotate forever.imageplanet、cometA class of starsSpaceIf they move in the middle, they will maintain their tracks for a longer time.Here, Newton did not mention the relationship between Newton's first law and the inertial reference system. What he focused on was why, in general observation, objects in motion would eventually stop moving?
He believes that the reason is that there are air resistance, ground friction, etc. acting on objects.If these forces do not exist, the moving object will never stop moving at a constant speed.This idea is a very important breakthrough, which requires extremely careful insight and rich imagination.
Newton's principle of inertia is one of the foundations of classical physics, and the understanding of the principle of inertia has changed with the development of modern physics.Newton said: "I just stand on the shoulders of giants!"
8. Mach
MachThis paper makes an important supplement to Newton's concept of inertia, and believes that inertia comes from the interaction between objects and the rest of the universe.(It is not only determined by the mass of the object itself).
9. Einstein and Theory of Relativity
An important progress in understanding inertia is the relationship between inertia and energy.
Albert EinsteinIn 1905, in the paper《On Electrodynamics of Moving Bodies》Proposed inSpecial relativityThis is a new physical theory, which is based on the inertia andInertial reference frame。It unifies the theory of mechanics and electromagnetism, and brings about a fundamental change in the concept of time and space.Einstein later proved thatMass energy relation，E=mc²A certain mass corresponds to a certain energy, whereas a certain energy corresponds to a certain mass.
Here, energy includes various forms of energy,BreachThe above understanding relates a certain form of energy and inertia.In this way, inertia is an attribute of energy, and energy has inertia (mass)Inertial massAll due to energy.As a basic concept of physics andAmount of substanceThe concept of mass ofmomentumThe concepts of mass and force are much more important than those of mass and force.
Although this epoch-making theory has actually changed many Newtonian concepts, such as mass, energy and distance, after that, Einstein's concept of inertia has no difference from Newton's original concept.In fact, the whole theory is based on Newton's definition of inertia.But it also makes special relativityPrinciple of relativityCan only be applied toInertial reference frame。In this reference system, an object that is not subject to external forces must remain stationary orUniform linear motionStatus.
To deal with this limitation, Einstein published a paper in 1916Foundations of General RelativityproposeGeneral relativity。This theory can be applied to non inertial reference systems.However, in order to achieve this goal, Einstein found that he must useCurved spacetimeInstead of traditionalNewtonian forceTo redefine several basic concepts (such asgravitation）。
Because of this redefinition, Einstein alsoGeodesic errorRedefining the concept of inertia has led to some subtle but important results.According to the general theory of relativity, when dealing with large-scale problems, traditional Newton inertia cannot be used and relied on.Fortunately, the special theory of relativity is still applicable to the spatiotemporal region that is small enough, and the connotation and work of inertia are still the same as those of the classical model.
Another profound result of special relativity is that,Energy and mass are not mutually independent physical properties, but can be converted each other.This new relationship also gives new meaning to the concept of inertia.The logical result of special relativity is that if the mass obeys the principle of inertia, the energy must also obey the principle of inertia.For many situations, this theory greatly broadens the definition of inertia and can be applied to matter and energy.
The inertia of energy broadens the understanding of inertia and energy.The major practical value it brings isnuclear energyRelease of.stayFission reactionMedium,Fission productIs less than the static mass of the material before fission,Quality lossRelease a large amountFission energy；stayFusion reactionThe net mass of fusion products is less than the net mass of substances before fusion, and mass loss releases a large amount ofFusion energy。It also makes people know a lotphysical phenomenon, including those involving all mass and energy conversion of substancesAntiparticle pairGeneration andannihilationProcess.
As we know, the inertial mass is a measure of the inertia of an object, reflecting the impedance of the object to accelerationGravitational massIt is a measure of the gravitational properties of objects, reflecting the ability of objects to generate and withstand gravity.They are obviously two completely different properties of matter. Whether the quantities describing the two different properties of matter are strictly equal is a problem. The equality of inertial mass and gravitational mass is a strict law.originalNewtonian mechanicsIndescribable inInertial massBeing equal to gravitational mass is no longer a universal fact dissociated from physics, but becomessignificanceSignificantGeneral relativityThe cornerstone of.EinsteinFinding this cornerstone and thus developing the general theory of relativity is really Einstein's unique insight and outstanding contribution.The problem of inertia has become a difficult problem for modern physics scholars, despite the great man Newton's classical theory.But in the age of science and technology, there are many phenomena that cannot be explained by previous theories.Use the past classics that cannot be explained.Einstein, the founder of modern physics, left us a question.Einstein was unable to explain inertia, so he reluctantly divided relativity into broad and narrow senses.His life has been plagued by this question or there is no answer.[4]
Discrimination and difference
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Difference from "First Law"
"Inertia" and "law of inertia" are not the same concept and cannot be confused.Their difference: inertia is an inherent property of all objects, which does not change according to external (force) conditions, and it always exists with objects.Newton's first lawIt is a law of motion that studies how an object moves when it is not affected by external forces. It points out the reason why "an object keeps moving at a constant speed in a straight line or in a static state".Inertia is that "the object has the characteristics of maintaining the original uniform linear motion state or static state";The two are completely different.The reason why Newton's first law is also called the law of inertia is that the phenomenon described in the law is a manifestation of the inertia of an object. When an object is subjected to an external force (the combined external force is not zero), the object cannot maintainUniform linear motionState or static state, but the property (inertia) that the object tries to keep the original motion state unchanged is still shown.
Difference from "force"
"Inertia" and "force" are not the same concept. "The bullet will continue to move forward after leaving the muzzle" and "the moving car on the horizontal road will move forward after the engine is turned off" are all inertia.The difference between inertia and force:
① Different physical meanings;Inertia means that the object has the property of keeping still or moving at a constant speed in a straight line;Force refers to the action of objects on objects.Inertia is an attribute of the object itself, which always has this property and is independent of external conditions;Force only exists when objects interact with each other. It doesn't matter if you leave the object.
② The elements are different: inertia has only size, no direction and action point, and size has no specific value and no unit;Force is composed of three elements: size, direction and action point. Its size has specific values, and the unit is cattle.
③ Inertia is the property of keeping the motion state of objects unchanged;The force action is to change the motion state of the object.
④ The magnitude of inertia is only related to thequalityThe force is related to many factors (depending on the type of vision).[5]
Difference from "speed"
The inertia has nothing to do with the speed of motion."The faster a car travels, the greater its inertia" is incorrect.A fast moving car is difficult to brake because the faster it moves, the harder it is to change the movement state of the object.It can be seen that the inertia is not related to the motion state.The magnitude of inertia is only related to the mass of the object.[5]
The dialectical relationship between the inertia maintenance balance and the change caused by its role.
The unity of opposites between inertia and external force of objects forms various complex motions of macro objects.If there is no external force, the object will not have complex and diverse forms of motion;If there is no inertia, the change of the moving state of the object does not require the action of force.Only when we understand the dialectical relationship between inertia and external force, it is not difficult to explainInertial phenomenon。For example, "when the hammer is loose, hit one end of the hammer handle against an object for several times, and the hammer head can be tightly sleeved on the hammer handle". This is because both the hammer and the handle originally moved downward, and the handle was impacted by resistance on the object, changing its motion state, and then stopped moving. The hammer head remained in its original motion state without resistance, and continued to move downward, so that the hammer head was tightly sleeved on the hammer handle.
category
When there is no external force, all objects always keepUniform linear motionState or quiescent state.Here, static and uniform linear motion refer to absolute static and absolute uniform linear motion.That is to say, the law of inertia is relative to the absolute static system.It is not relative to relative static, nor is it relative to absolute uniform linear motion system.The law of inertia applies to all objects.The motion of all objects originates from stillness, from absolute stillness, and is relative to absolute stillness.Just because the scope of application of the law of inertia is all objects, the acceleration will be generated after the objects are forced. Because all objects are forced, all objects are variable speed, which is the reason why the objects comply with the law of inertia when they are not forced, and comply with Newton's second law and third law when they are forced.
The inertia we usually say refers to the inertia of the object relative to the reference frame, that is, when the object is not subject to external forces, it has the ability to keep static with the reference frame orUniform linear motionThe nature of.Therefore, all inertia in different inertial systems is different.In the inertial system, the object remains stationary due to inertia. In the view of another inertial system with uniform linear motion, it is the object that maintains uniform linear motion due to inertia.How can a stationary object move in a uniform straight line?It turns out that the inertial reference may be different in different inertial frames.Since all of them are forced and move at variable speeds, the so-called inertial frame is the choice here. All round objects can be inertial frames, and any object selected can be inertial frames.
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Mass and inertia
The qualitative definition of inertia is the property of the object resisting the change of momentum.This definition can be quantitatively extended to measure the resistance of objects to the change of momentum, which can be used for mathematical calculation.This measure is called the inertial mass, or simply the mass.Therefore, mass represents the quantity of matter. At the same time, mass is also a measure of inertia of objects.
The momentum equation expresses the relationship between the momentum p, mass m, and velocity v of an object:
p=mv
However, Newton's second law equation can also express the relationship between the force F of the object and the mass (inertia mass) m, acceleration a:
F=ma
According to this equation, given the force, the greater the mass, the smaller the acceleration.The mass given by the momentum equation is the same as that given by the Newton equation.Because, if the mass is independent of time and speed, the Newton equation can be derived from the momentum equation.
In this way, mass is a measure of the inertia of the object, that is, the resistance of the object to acceleration.The meaning of the word inertia of objects has changed from the original meaning - the tendency to maintain momentum to object resistancemomentumMeasurement of change.
Gravitational mass and inertial mass
Gravitational massThe only difference from the inertial mass is the measurement method.
The gravitational mass of an unknown object can be obtained by measuring and comparing the gravitational force felt by an object of unknown mass with that felt by an object of known mass.Typically, you can use thebalanceTo make measurements.The advantage of this method is that no matter where you are or where you are on the planet, you can use a balance to measure, because for any object, the gravitational field is the same.as long asgravitational fieldWithout change, the balance will measure the credible gravitational mass.However, near supermassive stars, for example,black holeorneutron starThis method cannot be used because the gradient of the gravitational field in this area is too steep, and the difference between the gravitational field at the left and right trays of the balance is too large, which exceeds the allowable error range.In weightlessness environment, this method cannot be used because the balance cannot make any comparison.
Apply a known force to an object with unknown mass, measure the acceleration generated, and then apply Newton's second law equation to obtain the inertial mass. The error is limited to the accuracy of measurement.When in the free fall condition, use this method to sit in a special seat, calledObject mass gaugeThe inertial mass of weightless astronauts can be measured.[6]
It is worth noting that the experimenter has not yet found out the difference between gravitational mass and inertial mass.The experimenter has completed many experiments to test the experimental values of the two, but the differences are within the experimental error margin.When Einstein created the general theory of relativity, he got great enlightenment from the fact that the gravitational mass was equal to the inertial mass.He assumed that the gravitational mass is the same as the inertial mass, and the acceleration produced by gravity isSpatiotemporal continuumThe result of the inner slope is like that of a sphere withhelical lineStyle RolldownInverted cone。[7]
Inertial reference frame
When describing the motion of an object, its physical behavior can only be shown in relation to a specific reference system.If an inappropriate reference frame is selected, the relevant laws of motion may be more complex. In the inertial reference frame, the form of mechanical laws is the simplest.From the inertial reference system, anyUniform linear motionThe reference system ofInertial reference frame, otherwise“Non inertial reference frame”。In other words, Newton's law satisfiesGalilean invarianceThat is, Newton's law remains unchanged in all inertial reference systems[8]。
The error of choosing fixed stars to approximate inertial reference system is quite small.For example, the earth's revolution around the suncentrifugal force, 30 million times greater than the centrifugal force generated by the sun's revolution around the center of the Milky Way Galaxy.Therefore, the sun is a good inertial reference system when studying the motion of stars in the solar system.The earth can also be regarded as an inertial reference system.The acceleration caused by the earth's rotation is 0.034 m · s on the earth's surface.Gravitational accelerationIt is about 288 times the rotational acceleration.The acceleration caused by the earth's revolution around the sun is 0.006m · s, which is even smaller.Therefore, the earth's rotation and revolution acceleration can be ignored.
Assume inEarth reference systemObserver A observed that a train presentedUniform linear motion, the reference system attached to this train (train reference system) is alsoInertial reference frame。Suppose that a sphere falls from a high place in the train carriage, and observer B in the train reference system observes the trajectory of the sphere as if the sphere would fall vertically when the train is stationary.From the earth reference system, before falling, the moving speed and direction of the ball and the train are the same. The inertia of the ball ensures that the ball and the train move at the same speed when moving in the direction of the train.Note that here, inertia rather than mass gives this guarantee.
The observer in every inertial reference frame will observe that all physical behaviors comply with the same physical laws.From an inertial reference frame, it can be easily and intuitively transformed（Galileo transformation）To another inertial reference system.Thus, inEarth reference systemObserver A of the train can infer that observer B of the train reference system will observe that the ball falling in the train carriage will fall vertically.
aboutNon inertial reference frameAs the acceleration of the reference system is not equal to zero, the object will feelFictitious force。If the train is accelerating, observer B of the train reference system will observe that the ball will not fall vertically, but will change direction. This is because the ball and the train are moving at different speeds when moving in the direction of the train.
Let's take another example. If we take the rotation of the earth into consideration, the earth will rotate once every 24 hoursEarth reference systemRight and wrongInertial reference frame。When a missile is launched from the North Pole and aimed at a point P in the south at the equator, it is observed from the earth reference systemCoriolis force, this missile will deviate from point P.However, from the solar reference system, due to the rotation of the earth, the position of point P has changed, so it is not accurate to reach point P.
example
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one
The darts continue to move after they are released;
two
The dog shakes its body and shakes off the water on its fur (the washing machine dries);
three
The thrust required for launching a satellite is not only related to the gravity of the satellite and the inclination of the launch, but also to the launch direction and the latitude of the launch site. According to a point on the equator, the earth rotates at a speed of 460m/s from west to east.If the rocket is launched eastward, it can be usedearth rotationInertia savings ofThrust.With the change of the earth's latitudeLinear velocityIt is also different. The linear velocity of the earth rotation isequatorIt is the largest in North and South Poles, and the smallest in North and South Poles, almost zero.Therefore, the higher the latitude of the launch site, the greater the rocket thrust required.It is most labor-saving to launch along the direction of the earth's rotation near the equator;
four
The flywheel of the automobile engine provides the power of non power stroke;
five
Football flies in the air;
six
The paper plane continued to fly after leaving the hand;
seven
Once the interstellar detector is out of the gravity range of the earth, it can keep flying without using an engine. Gravity provides centripetal force to make uniform circular motion;
eight
If the hammer head is loose, as long as the hammer handle is hit on the fixed object several times, the hammer head will be firmly sleeved on the hammer handle;
nine
In the long jump, use the run-up to make yourself jump farther;
ten
When the car starts, people will lean back;When stopping, move forward;Turn left, people turn right;Turn right and people turn left (in fact, people always move forward relative to the ground, just because the direction of the car changes, people seem to change their position);
eleven
When emergency braking, people will lean forward;
twelve
Remove the dust on the clothes by "patting";
thirteen
Use a shovel to feed coal into the boiler;
fourteen
The bullet will continue to move forward after leaving the muzzle;
fifteen
When walking, my feet were caught by branches, etc.As the foot encounters resistance, it immediately stops moving, while the upper body continues to move forward due to inertia, so it will fall forward;;
sixteen
After the gas is turned off, the iron pan will continue to heat for a period of time before gradually cooling down, which is a "inertia" phenomenon of heat;
seventeen
When the car is running at high speed, the emergency brake is not to stop immediately, but to stop after taxiing for a certain distance;
eighteen
Water spray gun, water can continue to move after leaving the gun;
nineteen
When throwing the shot, the shot will continue to move after leaving the hand.[2]
Fallible point
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It is often said that "an object is subject to inertia (force)" or "due to inertia", which is wrong.It should be said that the object has inertia (or because of inertia).Scientists have also used inertia as an imaginary force.
All objects have inertia, which has nothing to do with whether they are moving or under force. It is an attribute of objects.The object has the attribute of maintaining the original motion (or static) state, which is called inertia.All objects have inertia.(It can be understood that static is also a kind of inertia)
Moment of inertia
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Moment of Inertia is the inertia of a rigid body when it rotates around an axis (the rotating object maintains itsUniform circular motionOr static characteristics), represented by the letter I or J.The role of moment of inertia in rotating dynamics is equivalent to the mass in linear dynamics, which can be formally understood as the inertia of an object for rotating motion, and is used to establish the relationship between several quantities such as angular momentum, angular velocity, torque and angular acceleration[9]。Moment of inertia is another form of inertia, which meansrigid bodyThe tendency to maintain a uniform rotational motion while rotating.Unless there isExternal momentImposed, rigidangular momentumNo change.This theory is calledConservation law of angular momentum。becausegyroscopeIt can resist any change in the direction of the rotation axis.
Possible causes
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The following conclusions are still controversial
The researchers propose that the possible cause of inertia can be explained by general relativity: the static is constant because the static mass will distort space-time and create a depression, just like an iron ball placed in the center of a spring bed to create a depression. This depression limits the movement of the iron ball and fixes its position, which can explain why the gravitational mass is exactly equal to the inertial mass, so the static is constant.The reason why the mover is always moving is that general relativity has rotating frame dragging and linear frame dragging. When a mass object rotates, space-time will follow the rotation, and when it moves in a straight line, space-time will follow the straight line movement. According to the reference frame dragging formula, the amplitude of space-time field movement is proportional to angular momentum or momentum,When spacetime rotates, the objects on it will follow the rotation, and when spacetime moves linearly, the objects will follow the forward movement. When the object rotates again or moves in a straight line, it will drive spacetime to rotate or move in a straight line. Such endless positive feedback results in the constant motion of the mover and the constant rotation of the mover, which is also the reason for the conservation of momentum and angular momentum,Therefore, the momentum is the inertia of the linear motion of the object and the angular momentum is the inertia of the rotating motion of the object.
