Decentralized constant formula

1. Decentralization is a phenomenon or structure, but the best explanation for this phenomenon is the concept of blockchain. If you want to have a thorough understanding, you can go to the community app of lianpai to have a look

2. Decentralized computing, also known as decentralized computing, allocates hardware and software resources to each indivial workstation or office. In contrast, centralized computing exists when most functions are performed, or is obtained from remote centralized locations. Distributed computing is a trend in modern business environment. This is contrary to the centralized computing popular in the early days of computer. The distributed computer system has many advantages over the traditional centralized network. The development of desktop computers is so rapid that their potential performance far exceeds the requirements of most commercial applications. This causes most desktop computers to remain idle (relative to their full potential). Decentralized systems can use the potential of these systems to maximize efficiency.

3. In other words, pluralism allows all kinds of thoughts or behaviors to coexist and no longer act according to the central idea of unity.

4. According to Hou Jietai: the so-called centralization refers to subtracting the mean value of a variable from its expected value. For sample data, each observation value of a variable is subtracted from the sample average value of the variable, and the transformed variable is centralized
for your question, subtract the mean from each measurement.

5.

Centripetal force formula:

extended data

generation of centripetal force:

because circular motion belongs to curvilinear motion, objects in circular motion will also be affected by external forces different from their velocity directions. For the object in circular motion, the centripetal force is a kind of pulling force, and its direction changes constantly with the movement of the object in the circular orbit. This pulling force points to the center of the circle along the radius of the circle, so it is called "centripetal force"

the centripetal force points to the center of the circle, and the object controlled by the centripetal force moves along the tangent direction, so the centripetal force must be perpendicular to the motion direction of the controlled object, and only proces the acceleration in the direction of the velocity normal

Therefore, the centripetal force only changes the direction of motion of the controlled object, but does not change the speed of motion, even in non-uniform circular motion. In the non-uniform circular motion, the tangential acceleration changing the velocity is not caused by the centripetal force

6. Physical quantity (unit) formula note formula deformation
velocity V (M / s) v = s: distance / T: time

gravity g (n) g = mg m: mass G: 9.8n/kg or 10N / kg
density ρ kg/m3 ρ= M / V M: mass V: Volume
resultant force F (n) direction is the same: F = F1 + F2
direction is opposite: F = F1-F2 direction is opposite, F1 & gt; F 2
buoyancy f floating
(n) f floating = g object - G view g view: gravity of object in liquid

buoyancy f floating
(n) f floating = g object this formula is only applicable to
floating or floating
buoyancy f floating
(n) f floating = g row = m row G= ρ Liquid GV discharge g discharge: gravity of discharged liquid
m discharge: mass of discharged liquid
ρ Liquid: density of liquid
v-row: volume of liquid
(i.e. volume immersed in liquid)
equilibrium condition of lever f1l1 = f2l2 F1: power L1: power arm
F2: resistance L2: resistance arm
fixed pulley f = g object
s = H F: tension on free end of rope
G object: gravity of object
s: distance of free end of rope moving
H: object lifting High distance
moving pulley f = (g object + G wheel)
s = 2 h g object: gravity of object
G wheel: gravity of moving pulley
pulley block f = (g object + G wheel)
s = n H N: number of segments of rope passing through the moving pulley
mechanical work w
(J) w = FS F: force
s: distance of moving in the direction of force
useful work w have
total work w have = G object h
W total = FS It is suitable for
mechanical efficiency when pulley block is placed vertically η= × 100%

power P
(W) P =
W: work
t: time
pressure P
(PA) P =
F: pressure
s: stressed area
liquid pressure P
(PA) P= ρ gh ρ： Density of liquid
H: depth (vertical distance from the liquid surface to the desired point)
heat Q
(J) q = cm △ T C: specific heat capacity m: mass
△ T: temperature change value
heat released by fuel combustion Q (J) q = MQ M: mass
Q: calorific value
common physical formula and important knowledge points
I. physical formula



/ >Unit) formula remarks formula deformation

series circuit
current I (a) I = I1 = I2 =... Current is equal everywhere
series circuit
voltage U (V) u = U1 + U2 +... Series circuit plays the role of
voltage dividing
series circuit
resistance R Ω R = R1 + R2 +...
parallel circuit
current I (a) I = I1 + I2 +... Main circuit current is equal to the sum of branch currents (shunt)
parallel circuit
voltage U (V) u = U1 = U2 =...
parallel circuit
resistance R Ω = + +…… < Ohm's law I =
the current in the circuit is proportional to the voltage, It is inversely proportional to resistance
current definition formula I =
Q: amount of charge (Coulomb)
t: time (s)
electric work w
(J) w = uit = Pt U: voltage I: current
t: time p: electric power
electric power P = UI = I2R = U2 / r u: voltage I: current
R: resistance
relationship between wave velocity and wave length and frequency C= λν C:

physical quantity unit formula
name symbol name symbol
mass m kg kg m = PV
temperature T ° C ° C
velocity v m / s, v = s / T
density p kg / M & sup3; kg/m³ P = m / V
force (gravity) f Newton (n) n g = mg
pressure P Pascal (PA) P P = f / s
work w Joule (J) w = FS
power P watt (W) W P = w / T
current I ampere (a) a i = u / R
voltage U volt (V) u = IR
resistance R ohm (Ω) r = u / I
electric work w Joule (J) w = uit
electric power P Watt (watt) W P = w / T = UI
heat Q Joule (joule) J Q = cm (T-T) °)
specific heat C coke / (kg ° C J/(kg ° C)
the speed of light in vacuum is 3 × 108m / s
G 9.8n/kg
15 ° C. sound speed in air 340m / s

junior high school physics formula compilation
[mechanics part]
1. Velocity: v = s / T
2. Gravity: g = mg
3. Density: v = s / T
2 ρ= M / V
4. Pressure: P = f / s
5. Liquid pressure: P= ρ GH
6. Buoyancy:
(1), f floating = f '- f (pressure difference)
(2), f floating = G-F (apparent gravity)
(3), f floating = g (floating, suspension)
(4), Archimedes principle: F floating = g row = ρ Liquid GV row
7. Lever balance condition: F1 L1 = F2 L2
8. Ideal slope: F / g = H / L
9. Ideal pulley: F = g / N
10. Actual pulley: F = (G + G moving) / N (vertical direction)
11. Work: w = FS = GH (lifting the object)
12. Power: P = w / T = FV
13. Principle of work: W hand = w machine
14 Actual machinery: wtotal = w + W extra
15 η＝ Wtotal
16. Efficiency of pulley block:
(1) η＝ G / NF (vertical direction)
(2) η＝ G / (G + G dynamic) (vertical direction without friction)
(3) η＝ F / NF (horizontal direction)
[thermal part]
1. Endothermic: q = cm (t-t0) = cm Δ T
2. Exothermic: q = cm (t0-t) = cm Δ T
3. Calorific value: q = q / M
4 η＝ Q efficient utilization / Q fuel
5. Heat balance equation: Q discharge = q suction
6. Thermodynamic temperature: T = t + 273k
[electrical part]
1. Current intensity: I = q electric quantity / T
2. Resistance: R= ρ L / s
3. Ohm's Law: I = u / R
4. Joule's Law:
(1), q = i2rt universal formula
(2), q = uit = Pt = UQ, electric quantity = u2t / R (pure resistance formula)
5. Series circuit:
(1), I = I1 = I2
(2), u = U1 + U2
(3), r = R1 + R2
(4), U1 / U2 = R1 / R2 (partial voltage formula)
(5) P1 / P2 = R1 / r2
6. Parallel circuit:
(1), I = I1 + I2
(2), u = U1 = U2
(3), 1 / r = 1 / R1 + 1 / r2 [R = r1r2 / (R1 + R2)]
(4), I1 / I2 = R2 / R1 (shunt formula)
(5), P1 / P2 = R2 / R1
(7) constant resistance:
(1), I1 / I2 = U1 / U2
(2), P1 / P2 = i12 / I22
(3), and P1 / P2 = U12 / u22
8 electric power:
(1), w = uit = Pt = UQ (universal formula)
(2), w = i2rt = u2t / R (pure resistance formula)
9 electric power:
(1), P = w / T = UI (universal formula)
(2), P = I2R = U2 / R (pure resistance formula)
[common physical quantity]
1, speed of light: C = 3 × 108m / S (in vacuum)
2. Sound velocity: v = 340m / S (15 ℃)
3. Distinguishing echo of human ear: ≥ 0.1s
4. Acceleration of gravity: g = 9.8n/kg ≈ 10N / kg
5. Standard atmospheric pressure:
760 mm, mercury column height = 1.01 × 105Pa
6 ρ＝ 1．0 × 103kg / m3
7. Freezing point of water: 0 ℃
8. Boiling point of water: 100 ℃
9. Specific heat capacity of water:
C = 4.2 × 103J/(kg• 6)
10, elementary charge: e = 1 × 10-19c
11. Voltage of a dry battery: 1.5V
12. Voltage of a lead-acid battery: 2V
13. Safety voltage for human body: ≤ 36V (not higher than 36V)
14. Voltage of power circuit: 380V
15. Voltage of home circuit: 220V
16. Unit conversion:
(1), 1m / S = 3.6km / h
(2), 1g / cm3 = 103kg / m3
(3), voltage of power circuit: 380V
15 1kw• h＝3．6 × 106J
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Author: JT Lijian 2007-2-28 20:06 reply to this speech
6 reply: junior high school physics formula
junior high school physics formula compilation
[mechanics part]
1. Velocity: v = s / T
2. Gravity: g = mg
3 ρ= M / V
4. Pressure: P = f / s
5. Liquid pressure: P= ρ GH
6. Buoyancy:
(1), f floating = f '- f (pressure difference)
(2), f floating = G-F (apparent gravity)
(3), f floating = g (floating, suspension)
(4), Archimedes principle: F floating = g row = ρ Liquid GV row
7. Lever balance condition: F1 L1 = F2 L2
8. Ideal slope: F / g = H / L
9. Ideal pulley: F = g / N
10. Actual pulley: F = (G + G moving) / N (vertical direction)
11. Work: w = FS = GH (lifting the object)
12. Power: P = w / T = FV
13. Principle of work: W hand = w machine
14 Actual machinery: wtotal = w + W extra
15 η＝ Wtotal
16. Efficiency of pulley block:
(1) η＝ G / NF (vertical direction)
(2) η＝ G / (G + G dynamic) (vertical direction without friction)
(3) η＝ F / NF (horizontal direction)
[thermal part]
1. Endothermic: q = cm (t-t0) = cm Δ T
2. Exothermic: q = cm (t0-t) = cm Δ T
3. Calorific value: q = q / M
4 η＝ Q efficient utilization / Q fuel
5. Heat balance equation: Q discharge = q suction
6. Thermodynamic temperature: T = t + 273k
[electrical part]
1. Current intensity: I = q electric quantity / T
2. Resistance: R= ρ L / s
3. Ohm's Law: I = u / R
4. Joule's Law:
(1), q = i2rt universal formula
(2), q = uit = Pt = UQ, electric quantity = u2t / R (pure resistance formula)
5. Series circuit:
(1), I = I1 = I2
(2), u = U1 + U2
(3), r = R1 + R2
(4), U1 / U2 = R1 / R2 (partial voltage formula)
(5) P1 / P2 = R1 / r2
6. Parallel circuit:
(1), I = I1 + I2
(2), u = U1 = U2
(3), 1 / r = 1 / R1 + 1 / r2 [R = r1r2 / (R1 + R2)]
(4), I1 / I2 = R2 / R1 (shunt formula)
(5), P1 / P2 = R2 / R1
(7) constant resistance:
(1), I1 / I2 = U1 / U2
(2), P1 / P2 = i12 / I22
(3), and P1 / P2 = U12 / u22
8 electric power:
(1), w = uit = Pt = UQ (universal formula)
(2), w = i2rt = u2t / R (pure resistance formula)
9 electric power:
(1), P = w / T = UI (universal formula)
(2), P = I2R = U2 / R (pure resistance formula)
[common physical quantity]
1, speed of light: C = 3 × 108m / S (in vacuum)
2. Sound velocity: v = 340m / S (15 ℃)
3. Distinguishing echo of human ear: ≥ 0.1s
4. Acceleration of gravity: g = 9.8n/kg ≈ 10N / kg
5. Standard atmospheric pressure:
760 mm, mercury column height = 1.01 × 105Pa
6 ρ＝ 1．0 × 103kg / m3
7. Freezing point of water: 0 ℃
8. Boiling point of water: 100 ℃
9. Specific heat capacity of water:
C = 4.2 × 103J/(kg• 6)
10, elementary charge: e = 1 × 10-19c
11. Voltage of a dry battery: 1.5V
12. Voltage of a lead-acid battery: 2V
13. Safety voltage for human body: ≤ 36V (not higher than 36V)
14. Voltage of power circuit: 380V
15. Voltage of home circuit: 220V
16. Unit conversion:
(1), 1m / S = 3.6km/h
(2), 1g / cm3 = 103K

7. Physical quantity unit formula
name symbol
mass m kg kg m = PV
temperature T ° C ° C
velocity v m / S M / S v = s / T
density p kg / M; kg/m³ P = m / V
force (gravity) f Newton (n) n g = mg
pressure P Pascal (PA) P P = f / s
work w Joule (J) w = FS
power P watt (W) W P = w / T
current I ampere (a) a i = u / R
voltage U volt (V) u = IR
resistance R ohm (Ω) r = u / I
electric work w Joule (J) w = uit
electric power P Watt (watt) W P = w / T = UI
heat Q Joule (joule) J Q = cm (T-T) °)
specific heat C coke / (kg ° C J/(kg ° C)
the speed of light in vacuum is 3 × 108m / s
G 9.8n/kg
15 ° C. sound speed in air 340 m / s
safe voltage not higher than 36 V
Outline of basic concepts of junior high school physics; Measuring tool: scale; When measuring, the next digit of the minimum scale should be estimated; The unit of light year is the unit of length< Time t: primary unit: second; Measuring tools: clocks and watches; Stopwatch is used in the laboratory. 1 hour = 3600 seconds, 1 second = 1000 milliseconds< 3. Mass m: the amount of substance in an object is called mass. Main unit: kg; Measuring tool: scale; Tray balance for laboratory use< (1) mechanical movement: movement in which the position of an object changes
reference: to judge the motion of an object, another object must be selected as the standard. The object selected as the standard is called reference< (2) uniform linear motion:
① two ways to compare the speed of motion: A. compare the distance passed in the same time. B compare the time required to travel the same distance
② formula: 1 m / S = 3.6 km / h< Force F: force is the action of an object on an object. The forces between objects are always mutual
unit of force: Newton (n). Instrument for measuring force: dynamometer; The laboratory uses spring scales
the effect of force: make the object deform or change the motion state of the object
the change of object motion state refers to the change of object velocity or motion direction
2. The three elements of force: the size, direction and action point of force are called the three elements of force
the diagram of force should be scaled; A schematic diagram of the force without scale< Gravity g: the force exerted on an object e to the attraction of the earth. Direction: vertical down
relationship between gravity and mass: g = mg, M = g / g
G = 9.8 N / kg. Pronunciation: 9.8 N / kg, which means the mass is 1 kg, and the gravity of the object is 9.8 n< Center of gravity: the point where gravity acts is called the center of gravity of an object. The center of gravity of a regular object is in the geometric center of the object< (4) two force equilibrium conditions: acting on the same object; The two forces are equal in magnitude and opposite in direction; Acting on a straight line
under the balance of two forces, an object can be stationary or move in a straight line at a constant speed
the equilibrium state of an object means that the object is in a state of static or uniform linear motion. The resultant force of the external force on an object in equilibrium is zero
5. Combination of two forces on the same line: same direction: resultant force F = F1 + F2; The direction of resultant force is the same as that of F1 and F2
the direction is opposite: the resultant force F = F1-F2, and the resultant force direction is the same as that of the large force
⒍ under the same conditions, rolling friction is much smaller than sliding friction
the sliding friction is related to the normal pressure, material properties and roughness of the contact surface Newton's first law is also known as the law of inertia. Its content is that all objects always keep static or uniform linear motion when they are not affected by external forces. Inertia: the object has the property of keeping the original static or uniform linear motion state, which is called inertia< Density
1 ρ： The mass per unit volume of a substance, density is a property of matter
formula: M= ρ V International Unit: kg / m3, common unit: g / cm3,
relation: 1g / cm3 = 1 × 103 kg / m3; ρ Water = 1 × 103 kg / m3
pronunciation: 103 kg / m3, which means the mass of 1 m3 of water is 103 kg< Density measurement: measure mass with pallet balance and volume of solid or liquid with measuring cylinder
area unit conversion:
1cm2 = 1 × 10-4 m2,
1 mm2 = 1 × 10-6 m2< Pressure P: the pressure on the unit area of an object is called pressure
pressure F: force acting vertically on the surface of an object, unit: n
the effect of pressure is expressed by the pressure, which is related to the pressure and the stressed area
pressure unit: n / m2; Special name: Pascal (PA)
formula: F = PS [S: stress area, common part of two objects in contact; Unit: m2
the methods to change the pressure are as follows: (1) the pressure can be reced by recing the pressure or increasing the stress area; ② Increasing the pressure or decreasing the stress area can increase the pressure< (2) internal pressure of liquid: [measurement of internal pressure of liquid: use liquid manometer (U-tube manometer).]
causes: e to the gravity of the liquid, pressure is generated on the bottom of the container; Due to the fluidity of the liquid, pressure is proced on the wall
rule: ① at the same depth, the pressure in all directions is equal; ② the greater the depth, the greater the pressure; ③ different liquids at the same depth, the higher the liquid density, the greater the pressure[ Depth h, the vertical height from the liquid level to a certain point of the liquid
formula: P= ρ GH H: unit: meter; ρ： Kg / m3; 8 N / kg< 3. Atmospheric pressure: the atmospheric pressure is proced by gravity. It is the madeburg hemispheric experiment that proves the existence of atmospheric pressure. It is Torricelli (Italian scientist) who determines the value of atmospheric pressure. The height of mercury column remains unchanged and the length of mercury column becomes longer after the torrix tube is tilted
1 standard atmospheric pressure = 76cm mercury column height = 1.01 × 105 PA = 10.336 m water column height
instruments for measuring atmospheric pressure: Barometer (mercury barometer, box barometer)
variation of atmospheric pressure with altitude: the higher the altitude is, the lower the atmospheric pressure is, that is, the higher the altitude is, the lower the boiling point is< Buoyancy and its causes: the buoyancy of an object immersed in liquid (or gas) is called buoyancy when it is supported upward by liquid (or gas). Direction: vertical upward; Cause: the pressure difference between the liquid and the object
2. Archimedes principle: an object immersed in liquid is subject to upward buoyancy, and the buoyancy is equal to the gravity of the object expelling the liquid
that is, f floatation = g liquid discharge = ρ Liquid GV discharge The formula for calculating buoyancy: F floating = G-T = ρ When the object floats: F floats = g object and ρ Things & lt; ρ Liquid when the object is suspended: F floating = g object and ρ Things= ρ Liquid
when the object floats up: F floats & gt; G and ρ Things & lt; ρ Liquid when an object sinks: F floats & lt; G and ρ Things & gt; ρ Liquid
7. Simple machine
1. Lever equilibrium condition: f1l1 = f2l2. Arm of force: the vertical distance from fulcrum to action line of force
the purpose of making lever in water position by adjusting nuts at both ends of lever is to directly measure the length of power arm and resistance arm
fixed pulley: equivalent to equal arm lever, can not save effort, but can change the direction of force
movable pulley: it is equivalent to the lever with power arm twice as much as resistance arm, which can save half of the force, but can't change the direction of force< 2. Work: two essential factors: 1. The force acting on the object; 2; ② The object passes the distance in the direction of force. W = FS, unit of work: Joule
3. Power: work done by an object in unit time. A physical quantity that represents the speed of work done by an object, that is, a high-power object does fast work
W = unit of Pt P: Watt; The unit of W is Joule; The unit of T is seconds< (1) the linear propagation of light: light propagates along a straight line in the same homogeneous medium. Pinhole imaging, shadow and spot are the linear propagation phenomena of light
the maximum velocity of light in vacuum is 3 × 108m / S = 3 × 105 km / s
2. The law of light reflection: one side, two sides, three equal The angle between the incident light and the normal is the angle of incidence. The angle between the reflected light and the normal is the reflection angle
planar mirror imaging features: virtual image, equal size, equal distance, symmetrical with the mirror. The reflection of objects in water is a reflection phenomenon of light< 3. Refraction of light: the virtual image of chopsticks and fish in water is the refraction of light
convex lens can converge light, concave lens can diverge light. The refraction law of light: one side, two sides, three with big four, big space< (4) the imaging law of convex lens: [when u = f, no imaging; when u = 2F, v = 2F, inverted image]
property of object distance u image distance V image light path diagram application
U & gt; 2f f< v< 2F inverted zoom camera
F & lt; u< 2f v> 2F inverted magnifying slide projector
U & lt; F magnifying positive and virtual magnifying glass
5 convex lens imaging experiment: place the candle, convex lens and light screen on the light holder in turn, so that the center of candle flame, convex lens and light screen are at the same height< 9. Thermology:
1. Temperature T: indicates the degree of coldness and hotness of an object It is a quantity of state
common thermometer principle: according to the property of liquid expansion and contraction
the differences between thermometer and thermometer are: ① range, ② minimum scale, ③ glass bubble, bending tube, and ④ usage< 2. Heat transfer condition: temperature difference. Heat: the amount of heat absorbed or released by an object ring heat transfer There are three ways of heat transfer: conction (heat is transferred along the object), convection (heat is transferred by the flow of liquid or gas) and radiation (heat is directly emitted from high temperature object)< Vaporization: the phenomenon that a substance changes from a liquid state to a gas state. Method: evaporation and boiling, vaporization should be endothermic
factors affecting evaporation speed: ① liquid temperature, ② liquid surface area, ③ air flow on liquid surface. Evaporation has cooling effect< Specific heat capacity C: the specific heat capacity of a substance per unit mass, which is the heat absorbed when the temperature rises by 1 ℃
specific heat capacity is one of the characteristics of materials, unit: coke / (kg ℃). The specific heat capacity of water in common materials is the largest
C water = 4.2 × 103 J / (kg ℃): 4.2 × 103 joules per kilogram centigrade
physical meaning: it means that the mass of water is 1kg, the heat absorbed by 1 ℃ is 4.2kg × 103 joules
5. Heat calculation: Q discharge = cm ⊿ t drop, Q suction = cm ⊿ t rise
q is directly proportional to C, m, ⊿ T, and inversely proportional to C, m, ⊿ t. ⊿ t = q / cm
6. Internal energy: the sum of kinetic energy and molecular potential energy of all molecules in the body. All objects have internal energy. Internal energy unit: Joule
the internal energy of an object is related to the temperature of the object. The internal energy increases with the increase of temperature; The internal energy decreases with the decrease of temperature
the method of changing the internal energy of a body: work and heat transfer (equivalent to changing the internal energy of a body)
7. The law of energy conversion and conservation: energy will neither be generated nor disappear out of thin air, it will only change from one form to another

9. Row V ÷ V = P ÷ P liquid (f floating = g substance)
V dew ÷ V row = P liquid-p substance ÷ P
V ÷ V substance = Liquid P substance ÷ When p liquid
V row = V substance, G ÷ F = P ÷ P liquid
physical theorem, law and formula table The motion of particles (1) ---- linear motion
1) uniformly variable speed linear motion
1. Average velocity V flat = s / T (definition)
2. Useful inference VT ^ 2-VO ^ 2 = 2As
3. Middle time velocity V T / 2 = V flat = (VT + VO) / 2
4. Final velocity V T = VO + at
5. Middle position velocity V S / 2 = [(VO ^ 2 + VT ^ 2) / 2] ^ (1 / 2)
6. Displacement S = V flat t = V flat T + (at ^ 2) / 2 = V T / 2T
7. Acceleration a = (VT VO) / T {with VO as the positive direction, a and VO in the same direction (acceleration) a & gt; 0 In reverse, a & lt; 0}
8 Δ s＝aT^2 ｛ Δ S is the difference of displacements in consecutive adjacent equal time (T)}
9. Main physical quantity and unit: initial velocity (VO): M / S; Acceleration (a): M / S2; Final velocity (VT): M / S; Time (T) seconds (s); Displacement (s): m; Distance: meters; Speed unit conversion: 1m / S = 3.6km/h
note:
(1) the average velocity is a vector
(2) the acceleration is not necessarily large when the velocity is large
(3) a = (VT VO) / T is only a measure, not a determinant
(4) other related contents: particle, displacement and distance, reference frame, time and time [see Volume I P19] / S-T diagram, V-T diagram / speed and speed, instantaneous speed [see Volume I p24]
2) free falling body motion
1. Initial velocity VO = 0
2. Final velocity VT = GT
3. Falling height h = GT2 / 2 (calculated from VO position downward)
4. Dection VT ^ 2 = 2GH
note:
(1) free falling body motion is a uniformly accelerated linear motion with zero initial velocity and follows the law of uniformly variable speed linear motion
(2) a = g = 9.8 m / S2 ≈ 10 m / S2 (the acceleration of gravity is smaller near the equator, and it is smaller in the high mountains than in the plain, and the direction is vertical and downward)
3) vertical throwing motion
1. Displacement S = VOT - (GT ^ 2) / 2
2. Final velocity VT = VO GT (g = 9.8m / S2 ≈ 10m / S2)
3. Useful inference vt2-vo2 = - 2GS
4. Maximum rising height Hmax = VO ^ 2 / 2g (from throwing point)
5. Round trip time t = 2VO / g (time from throwing out to original position)
note:
(1) whole process processing: uniform deceleration straight-line operation The acceleration is negative
(2) segmented processing: upward is uniform deceleration linear motion, downward is free falling motion, with symmetry
(3) the rising and falling processes are symmetrical, such as the velocity equivalent at the same point and the opposite direction
2. Motion of particles (2) --- curvilinear motion Gravity
1) horizontal throwing motion
1. Horizontal velocity: VX = VO
2. Vertical velocity: vy = GT
3. Horizontal displacement: x = VOT
4. Vertical displacement: y = GT ^ 2 / 2
5. Movement time: T = (2Y / g) 1 / 2 (usually (2H / g) 1 / 2)
6. Combined velocity: VT = radical (VX ^ 2 + vy ^ 2) = radical [VO ^ 2 + (GT) ^ 2] (combined velocity direction and direction) Horizontal angle β: tg β＝ Vy / VX = GT / V0)
7. Combined displacement: S = root sign (x ^ 2 + y ^ 2) (angle between displacement direction and horizontal) α: tg α＝ Y / x = GT / 2VO)
8. Horizontal acceleration: ax = 0; The acceleration in vertical direction: ay = g
note:
(1) the horizontal projectile motion is a curve motion with uniform velocity change, and the acceleration is g, which can be generally regarded as the combination of the horizontal linear motion with uniform velocity and the vertical free falling motion
(2) the movement time is determined by the falling height h (y) and has nothing to do with the horizontal throwing speed< br /> 3 θ And β The relationship between them is TG β＝ 2tg α
(4) time t is the key to solve the problem 5) When the direction of velocity is not in the same line as the direction of resultant force (acceleration), the object will move in a curve
2) uniform circular motion
1. Linear velocity v = s / T = 2 π R / T
2. Angular velocity ω＝Φ/ t＝2 π/ T＝2 π F
3. Centripetal acceleration a = V2 / r = ω 2r＝(2 π/ T) 2R
4. Centripetal force fcenter = MV2 / r = m ω 2r＝mr(2 π/ T)2＝m ω 5. Period and frequency: T = 1 / F 6. Relationship between angular velocity and linear velocity: v = ω R
7. Relationship between angular velocity and rotational speed ω＝ two π Main physical quantities and units: arc length (s): meter (m); Angle Φ)： Radian (RAD); Frequency (f): Hz; Period (T): second (s); Speed (n): R / S; Radius (R): m; Linear velocity (V): M / S; Angular velocity ω： rad/s Centripetal acceleration: M / S2
note:
(1) the centripetal force can be provided by a specific force, a resultant force, or a component force. The direction is always perpendicular to the velocity direction and points to the center of the circle
(2) the centripetal force of an object in uniform circular motion is equal to the resultant force, and the centripetal force only changes the direction of velocity, but does not change the size of velocity, so the kinetic energy of the object remains unchanged, the centripetal force does not do work, but the momentum changes constantly< Kepler's third law: T2 / R3 = K (= 4) π 2 / GM) {R: orbital radius, t: period, K: constant (independent of the mass of the planet, depends on the mass of the central celestial body)}
2. Law of gravitation: F = g (m1m2) / R ^ 2 (g = 6.67) × 3. Gravity and acceleration of gravity on celestial bodies: GMM / r2 = mg; GMM / r2 = mg; GMM / r2 = mg; GMM / r2 = mg; GMM / r2 = mg; GMM / r2 = mg; GMM / r2 = mg; G = GM / r2 {R: celestial body radius (m), M: celestial body mass (kg)}
4; ω＝ Root number (GM / R3); T = root ((4) π^ 5. The first (second and third) cosmic velocity V1 = (g earth r earth) 1 / 2 = (GM / R earth) 1 / 2 = 7.9km/s; V2＝11.2km/s V3 = 16.7km/s
6. GMM / (R + H) 2 = M4 π 2 (r earth + H) / T2 {h ≈ 36000km, H: height from the earth's surface, R earth: radius of the earth}
note:
(1) the centripetal force required for celestial body motion is provided by universal gravitation, f direction = f ten thousand
(2) the mass density of celestial bodies can be estimated by using the law of universal gravitation< (3) the geostationary satellite can only operate over the equator, and its operation cycle is the same as the earth rotation cycle
(4) when the orbit radius of the satellite becomes smaller, the potential energy becomes smaller, the kinetic energy becomes larger, the velocity becomes larger, and the period becomes smaller
(5) the maximum orbit speed and minimum launch speed of the earth satellite are 7.9km/s< (3) force (common force, composition and decomposition of force)
1) common force
1. Gravity g = Mg (vertical downward, g = 9.8m / S2 ≈ 10m / S2, acting point at the center of gravity, applicable to the earth's surface)
2. Hooke's law f = KX {direction along the recovery deformation direction, K: stiffness coefficient (n / M), X: deformation variable (m)}
3. Sliding friction f = μ FN {is opposite to the relative motion direction of the object, μ： Friction coefficient, FN: positive pressure (n)}
4. Static friction 0 ≤ F, static ≤ FM (opposite to the relative motion direction of the object, FM is the maximum static friction)
5. Gravitation f = gm1m2 / R2 (g = 6.67) × 6. Electrostatic force F = kq1q2 / R2 (k = 9.0) × 7. Electric field force F = EQ (E: field strength n / C, Q: electric quantity C, the electric field force of positive charge is the same as the direction of field strength)
8. Ampere force F = bilsin θ θ When l ⊥ B: F = bil, B / / L: F = 0)
9. Lorentz force F = qvbsin θ θ When v ⊥ B: F = QVB, V / / B: F = 0)
note:
(1) the stiffness coefficient K is determined by the spring itself
(2) friction coefficient μ It has nothing to do with the pressure and contact area, but is determined by the material characteristics and surface condition of the contact surface
(3) FM is slightly larger than that of FM μ FN, generally regarded as FM ≈ μ FN;
(4) other related contents: static friction (size and direction) [see P7 in Volume 1]
(5) symbol and unit of physical quantity B: magnetic inction intensity (T), l: effective length (m), I: current intensity (a), V: velocity of charged particle (M / s), Q: charge of charged particle (charged body) (c)
(6) the direction of Ampere force and Lorentz force are determined by left-handed rule< 2) the composition and decomposition of forces
1. The composition of forces on the same line is in the same direction: F = F1 + F2, reverse: F = F1-F2 (F1 & gt; F2)
2. Synthesis of mutual angular force:
F = (F12 + F22 + 2f1f2cos) α) 1 / 2 (cosine theorem) F1 ⊥ F2: F = (F12 + F22) 1 / 2
3. Range of resultant force: | F1-F2 | ≤ f ≤| F1 + F2 |
4. Orthogonal decomposition of force: FX = fcos β， Fy＝Fsin ββ Is the angle TG between the resultant force and the x-axis β＝ FY / FX)
note:
(1) the composition and decomposition of forces (vectors) follow the parallelogram rule
(2) the relationship between resultant force and component force is equivalent substitution relationship, which can replace the joint action of component force with resultant force, and vice versa
(3) in addition to the formula method, the drawing method can also be used to solve the problem. In this case, the scale should be selected and the drawing should be strict
(4) when the value of F1 and F2 is fixed, the angle between F1 and F2 is smaller α The larger the angle, the smaller the resultant force
(5) the combination of forces on the same straight line can take the positive direction along the straight line, and the direction of the force can be represented by a sign, which is simplified to an algebraic operation< (4) dynamics (motion and force)
1. Newton's first law (Law of inertia): an object has inertia and always keeps in a state of uniform linear motion or static until it is forced to change this state by an external force
2. Newton's second law of motion: F = ma or a = f = ma / MA {determined by the external force, Newton's third law of motion: F = - f '{negative sign means opposite direction, F and f' act on each other respectively, the difference between balance force and reaction force, practical application: recoil motion}
4. The balance of copoint force is f = 0, which generalizes {orthogonal decomposition method, three force confluence principle}
5. Overweight: FN & gt; G. Weight loss: FN & lt; G {acceleration direction downward, both weightless, acceleration direction upward, both overweight}
6. Applicable conditions of Newton's law of motion: applicable to solving low-speed motion problems, applicable to macro objects, not applicable to dealing with high-speed problems, not applicable to micro particles [see Volume I, p57]
note: equilibrium state means that objects are in a static or uniform linear state, Or rotate at a constant speed< Vibration and wave (mechanical vibration and propagation of mechanical vibration)
1. Simple harmonic vibration f = - KX {F: restoring force, K: proportional coefficient, X: displacement, negative sign indicates that the direction of F is always opposite to x}
2. Simple penlum period T = 2 π( L / g) 1 / 2 {L: penlum length (m), G: local gravity acceleration value, the tenable condition: penlum angle θ& lt; 100; l>& gt; R}
3. Vibration frequency characteristics: F = f driving force
4. Resonance conditions: F driving force = f solid, a = max, resonance prevention and application [see Volume I P175]
5. Mechanical wave, shear wave and longitudinal wave [see volume II P2]
6. Wave velocity v = s / T = λ f＝ λ/ In the process of t {wave propagation, a period propagates one wavelength forward; The wave velocity is determined by the medium itself}
7; 20℃:344m/s 30℃:349m/s( Acoustic wave is a longitudinal wave)
8. Obvious diffraction of wave (wave continues to propagate around the obstacle or hole) condition: the size of the obstacle or hole is smaller than the wavelength, or the difference is not significant
9. Interference condition of wave: the frequency of two waves is the same (the difference is constant, the amplitude is similar, and the vibration direction is the same)
10. Doppler effect: e to the interaction between the wave source and the observer

10.

De flow means that all social resources can be aggregated and distributed with one click

in a system with many nodes, each node has a high degree of autonomy. Nodes can connect with each other freely to form a new connection unit. Any node may become the stage center, but it does not have the mandatory central control function. The influence between nodes will form a nonlinear causal relationship through the network

This kind of open, flat and equal system phenomenon or structure is called decentralization

extended materials:

compared with the previous Internet (WEB 1.0) era, today's Internet (Web 2.0) content is no longer proced by professional websites or specific groups, but by the participation of the whole Internet users and the creation of equal power levels. Anyone can express their views on the Internet or create original content to proce information together

with the diversification of network service shape, the decentralized network model becomes more and more clear and possible. After the rise of Web2.0, the services provided by Wikipedia, Flickr, blogger and other network service providers are decentralized. Any participant can submit content, and Internet users can create or contribute content together