In general context, centrifugal force is not a real force.It is only used to rotate the reference system（Non inertial reference frame）Next,Newton's law of motionIt can still be used.stayInertial reference frameThere is no centrifugal force below. Inertial force is required only in non inertial reference systems (such as rotating reference systems), otherwise Newton's law of motion cannot be used.
Imagine a disk rotating around the center,angular velocityIs ω.There is a wooden block with a mass of m on the disk, which is connected by a rope. The other end of the rope is fixed at the center of the disk (also the center of rotation), and the length of the rope is r.The wood block rotates with the disk. Assuming that there is no friction, the rotation of the wood block is due to the tension of the rope.To the observer who rotates with the disk, the wood block is static.According to Newton's law, the resultant force on the wood block should be zero.But the wood block is only subjected to one force, that is, the pull of the rope, so the resultant force is not zero.So does this violate Newton's law?Newton's law only holds in the inertial system, but the reference system of the observer rotating with the disk is a non inertial system, so Newton's law does not hold here.In order to make Newton's law still hold in a non inertial system, it is necessary to quote an inertial force, that is, centrifugal force.The centrifugal force is equal to the tension provided by the rope, but in the opposite direction.After the introduction of centrifugal force, the observer who rotates with the disk sees that the wood block is subject to the tensile force and centrifugal force of the rope at the same time, the size is equal, the direction is opposite, and the resultant force is zero.At this time, the wood is still, and Newton's law holds.
Centrifugal motionIt refers to the phenomenon that objects move away from the center.CentrifugeIt is to use centrifugal movement to refine nuclear materials.
When the object is in non linear motion (non Newtonian environment, for example:Circular motionOr turning motion), because the object must have its own mass, the inertia caused by the mass will force the object to continue to move in the tangent direction of the motion track (the original straight direction of the instant forward), rather than in the direction of the next turning.
If there is a passenger on the object (such as a car) that is moving in a non straight line, the passenger will be subjected to the centripetal force provided by the car to the passenger because of the same turning motion with the car. However, if the passenger is taken as the reference system, the reference system isNon inertial frameHe will be subjected to a centripetal force pointing to the center of the circle from a car that is relatively stationary with him, but at the same time he will also give the car a reverse force of equal magnitude, pointing outward from the center of the circle, as if he would be thrown out without a car. This force is the so-called centrifugal force.
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Due to being inNon inertial frameIn this case, the force felt by the object is not real, so some people will call this phenomenon "centrifugal movement".
Relative to the object in the rotating non inertial system, the centrifugal force isF=mω^2r(where ω represents the self rotatingangular velocity）。It should be noted that the direction of the centrifugal force isalongradiusDeviation from the center。
(In the above formula, ω refers to the objectCircular motionOfangular velocity, r refers to the circular motion of the objectradius, T refers to the period of circular motion of the object, π refers toPi）
Centrifugal phenomenon
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Centrifugal phenomenon
Centrifugal force is a manifestation of inertia, which does not exist in fact.In order to make the object move in a circle, the object needs to be subjected to a force pointing to the center of the circle, that is, the centripetal force.If this object is used as the origin to establish coordinates, it seems that there is a force in the same direction as the centripetal force, which makes the object move away from the center of the circular motion.(When the force on the object is not enough to provide the centripetal force required for circular motion, it seems that the centrifugal force is greater than the centripetal force, and the object will move away from the center of the circle. This phenomenon is called“Centrifugal phenomenon”。）
It is assumed that if centrifugal force exists, it will be balanced with centripetal force, the force on the object will be balanced, the speed direction will not change, it is in a balanced state, and it is impossible to make circular motion, so it is proved that centrifugal force does not exist, that is, centrifugal force isEffect of forceTo name.
Note: Centrifugal force does not exist as inertial force in fact. Descartes, a great scientist and physicist, made this mistake in his theory of "vortex theory".Therefore, the following statement is wrong - "When an object moves in a circle, it is in its orbittangentThe direction is affectedTangential force, there is a component force acting in the centrifugal direction, so it is called centrifugal force. "
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satellite
On a celestial body, the satellite makes inertial motion at the edge of the main stargravitationThe satellite is bound to make a revolution. If the inertial motion force (speed) of the satellite is greater than the gravitational binding force of the main star, the satellite will be far away from the center.stayearthOn the other hand, the object makes inertial motion at the edge of the stationary center. Because the binding force of the object binds the object, the object rotates circumferentially. If the inertial motion force (speed) of the object is greater than the binding force of the object, the inertial motion object will move away from the center.(Since the binding force of water and gas is very low, they will both leave the center. Metals with high binding force will not be centrifuged.) - If "due to the low binding force of water, they will leave the center".Then the water should be poured into the sky instead of flowing into the sea at a low altitude.
Centrifugal force, which is caused by the change of the direction or speed of the circular motion objectinertia force。We know that when an object travels with one object, the speed of the two objects is the same, and the object being boarded moves forward inertia.When the object suddenly changes direction, the object being boarded will also move forward in inertia. The change of the movement direction will lead to the change of the combined external force, which will produce centrifugal force.
1、 Meteor hammer
Meteor hammer，It is a kind of soft hammer made by tying the metal hammer head to one end or both ends of the long ropeWeapon, also belongs to the category of cable concealed weapons.The rope with only one hammer is about five meters long, which is called "single meteor";The rope tied with two hammers is four and a half feet long, which is called "double meteor".The hammers are melon shaped, polyrhombic and round, and are as large as duck eggs.The end of the hammer body has an elephant nose eye, which is used to string links.moderna martial artDuring the exercise, double meteors are drilled, mainly holding the middle part of the rope for standing dance, lifting flower, one handed flowerPectoral flower, waist wrapping, neck wrapping, throwing, and other flower practices, which are the same as stick flower and broadsword flower.
2、 Tea paradox
The tea paradox describes the phenomenon that when the tea in the cup is stirred, the tea will swim back to the center of the bottom of the cup, instead of being pushed to the edge of the bottom of the cup by the spiral centrifugal force.The original explanation comes fromAlbert EinsteinIn 1926, a paper was written to explain the problem of bank erosion (Bayer's Law).Stir the liquid to make it rotate in the cup, generating outward centrifugal force.
However, due to the friction of the cup wall, the liquid near the outside of the bottom slows down its rotation, and the centrifugal force there weakens so that the effect of the pressure difference on the water flow is greater than the centrifugal force.This is calledboundary layerOr more accuratelyEkman layer。
Due to centrifugal force, the force along the edge is greater than that in the middle.If all the liquid as asolidFor rotation, the internal centripetal force is related to the external (centripetal force) and speed, so there is no inward or outward movement.
In a teacup, the rotation is slower at the bottom, and the pressure gradient produces and then produces inward waves along the bottom.Up a little, the liquid flows to the outside.This second wave current flows inward along the bottom to gather the tea leaves outside the edge to the center.Since the weight of tea leaves cannot rise, they stay at the bottom center.Combined with the effect of the first rotating wave current, these tea leaves will spiral inward along the bottom.
We usually do it on the groundReference systemIt can be assumed that the ground is stationary, or the ground movement is regarded asUniform linear motion, i.eInertial reference frame，NewtonIt was on this premise that the law of motion was summed up.If the reference system is variable speed, that isNon inertial reference frame，Newton's lawCan not be directly applied, so people imagine“inertia”To solve the application of Newton's law.Inertial centrifugal force is an imaginary force in non inertial system.Next liftUniform circular motionexample:
The linear velocity direction of uniform circular motion changes from time to time, indicating thatCentripetal acceleration, and the direction of centripetal acceleration also changes from time to time, which is a typical non inertial frame.If there is a big turntable workingUniform circular motionWhen you sit on the plate, do not look at the surrounding scenery, and put yourself in theNon inertial frameYou will definitely feel that there is some force that wants to push yourself down, but at this time there is no force applying object pushing you. This force is called inertial centrifugal force.
Finally, let me remind you that the so-called "inertial force" only exists in the non inertial system, which is a virtual force. It is a virtual force to extend Newton's law to the non inertial systemNewton's Third LawOutside,Newtonian mechanicsVarious laws and theorems in can be applied in non inertial frames.
