stayPhysicsIn science, the physical quantity of velocity is used to express the relativity of objectsreferenceThe speed of movement of objects (usually with the earth or the ground as the reference object).In physics, the moving speed of a particle to the ground or to a stationary object on the ground is generally called the relative speed;The motion speed of the particle to the moving reference system is calledAbsolute speed；The moving speed of the moving reference system to the ground is called the implicated speed.Absolute speed=Implicate speed+relative velocity(Since the speed is a loss, the vector synthesis method shall be used for the above operations. That istriangleRule, or squarerule。However, the above operations are applicable, and this rule can only be used in the macro low-speed state.) In astrophysics, the classical physical motion formula is not valid.
(Circumferential motion, w represents instantaneousangular velocity)
Physical unit
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SI unit m/s or m · s-1
Common unit in transportation: km/h or km · h-1
Conversion relationship: 1m/s=3.6km/h 1km/h=1/3.6m/s ≈ 0.28m/s. According to speed classification, movement can be divided into average speed, instantaneous speed, etc.According to the movement direction, it can be divided intoRectilinear motionAnd curvilinear motion.
Limit speed of human body
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Horse racing, skating, etc. fully demonstrate people's limits.
Movement speed
Cosmic velocity
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First cosmic velocity
(also called circumferential speed): refers to the speed at which objects move in a circle close to the earth's surface (also known asArtificial earth satelliteMinimum launch speed).The size is 7.9km/s - the calculation method is
(g is gravity acceleration, R is star radius)
Second cosmic speed
(also called breakaway speed): refers to the minimum initial speed required for an object to completely break away from the constraints of the earth's gravity and fly away from the earth.The size is 11.2km/s
Third cosmic speed
(also called escape speed): refers to the minimum initial speed required for an object launched from the earth to fly out of the solar system, free from the constraints of solar gravity.Its size is 16.7km/s.
Fourth cosmic speed
The so-called fourthCosmic velocityMeans that objects launched from the earth get rid of the gravitational binding of the Milky Way and fly outGalaxyThe minimum initial speed required, about 110-120km/s, refers to the navigation speed required in most parts of the Milky Way.If the rotation speed of the solar system around the silver center is fully utilized, the minimum sailing speed can be 82km/s.Since human beings know little about the Milky Way, it will take a long time for this number to form a public opinion.It refers to the departure speed required in most parts of the Milky Way.The fourth cosmic speed cannot be obtained at all, because the mass and radius of the silver core cannot be taken.
Fifth cosmic speed
Fifth cosmic speedIt refers to the minimum speed at which a spacecraft can fly out of the local galaxy group when it is launched from the earth. Since the radius and mass of the local galaxy group do not have enough accurate data, it is impossible to accurately know the data size.Scientists estimate that the local galaxy cluster is about 5-10 millionLight yearAccording to this calculation, it should take 1500 to 2250km/S to fly away, but at the level of human scientific development, it will take at least several hundred years to reach this speed, so it is just a fantasy.
