For junior high school all scientific calculation formula, whether it is chemical or physical, to be complete

For junior high school all scientific calculation formula, whether it is chemical or physical, to be complete

Deformation of remark formula of physical quantity (unit) formula
Speed v
（m/S） v=
S: Distance
t: Time
Gravity g
(N) G = mg m: mass
g: 8 N / kg or 10 N / kg
Density ρ
（kg/m3） ρ=
m: Quality
5: Volume
Resultant force
(N) Same direction: F = F1 + F2
Opposite direction: F = f 1-f 2 when the direction is opposite, F 1 > F 2
Buoyancy f
(N) F floating = g object - G view g view: gravity of object in liquid
Buoyancy f
(N) F = g, this formula is only applicable
Floating or levitating objects
Buoyancy f
(N) F floating = g row = m row, g = ρ liquid, GV row, g row: the gravity of the liquid
M row: the mass of liquid in row
ρ liquid: density of liquid
V row: volume of liquid to be discharged
(volume immersed in liquid)
Balance condition of lever f1l1 = f2l2 F1: power L1: power arm
F2: resistance L2: resistance arm
Fixed pulley f = g
S = H F: the tension on the free end of the rope
G object: the gravity of an object
S: The distance that the free end of the rope moves
h: The distance an object rises
Moving pulley f = (g object + G wheel)
S = 2 h g object: the gravity of the object
Wheel G: gravity of moving pulley
Pulley block f = (g object + G wheel)
S = N H N: the number of segments of the rope passing through the movable pulley
Mechanical work W
(J) W = FS F: force
s: The distance moved in the direction of the force
Useful work
Total work w total w = g matter H
Wtotal = FS, when the pulley block is placed vertically
Mechanical efficiency η = × 100%
Power p
（w） P=
W: Merit
t: Time
Pressure P
（Pa） P=
F: Pressure
S: Stress area
Liquid pressure P
(PA) P = ρ GH ρ: density of liquid
h: Depth (from liquid level to desired point)
The vertical distance of the
Heat Q
(J) Q = cm △ T C: specific heat capacity m: mass
Δ T: change value of temperature
Fuel emission
Q (J) q = MQ M: mass
q: Calorific value
Common physical formulas and important knowledge points
1、 Physical formula
Deformation of remark formula of physical quantity (unit) formula
Series circuit
Current I (a) I = I1 = I2 = The current is equal everywhere
Series circuit
Voltage U (V) u = U1 + U2 + Start of series circuit
Partial pressure action
Series circuit
Resistance R (Ω) r = R1 + R2 +
Parallel circuit
Current I (a) I = I1 + I2 + The main circuit current is equal to the current of each circuit
Sum of branch currents (shunt)
Parallel circuit
Voltage U (V) u = U1 = U2 =
Parallel circuit
Resistance R (Ω) = +
Ohm's law I=
Current and voltage in circuit
In direct proportion to the resistance
Current definition I=
Q: Charge quantity (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
Electromagnetic wave velocity and wave propagation
The relationship between length and frequency C = λ ν C: wave velocity (the wave velocity of electromagnetic wave is constant, equal to 3 × 108m / s)
λ: Wavelength V: frequency
2、 Knowledge points
1. Several values to remember:
a. Sound propagation speed in air: 340m / S B light propagation speed in vacuum or air: 3 × 108m / S
c. The density of water is 1.0 × 103kg / m3 D. the specific heat capacity of water is 4.2 × 103J / (kg ᦇ 8226; ℃)
e. Voltage of a dry battery: 1.5V F. voltage of household circuit: 220V
g. Safety voltage: not higher than 36V
2. Density, specific heat capacity and calorific value are the characteristics of a substance. The values of the three physical quantities of the same substance generally do not change. For example, a cup of water and a bucket of water have the same density and specific heat capacity,
3. A virtual image of equal size formed by a plane mirror. The image and the object are symmetrical about the plane mirror
3. Sound cannot be transmitted in vacuum, but light can be transmitted in vacuum
4. Ultrasound: sound with frequency higher than 2000, e.g. bat, ultrasound radar;
5. Infrasound: volcanic eruption, earthquake, wind explosion, tsunami can produce infrasound, nuclear explosion, missile launch can also produce infrasound
6. Light propagates along a straight line in the same homogeneous medium. Shadow, pinhole imaging, solar eclipse and lunar eclipse are all formed by light propagating along a straight line
7. When light is refracted, the angle in the air is always a little larger. When you look at the objects in the water, you can see a shallow virtual image
8. Convex lens converges and concave lens diverges
9. The law of convex lens imaging: the object forms a reduced and inverted real image outside the double focal length. Between the double focal length and the double focal length, the object forms an inverted and enlarged real image. Within the double focal length, the object forms an upright and enlarged virtual image
Sliding friction is related to pressure and surface roughness. Rolling friction is smaller than sliding friction
11. Pressure is a physical quantity to compare the effect of pressure. The effect of pressure is related to the size of pressure and the stressed area
12. When transmitting voltage, high voltage should be used to transmit electricity. The reason is that the loss of electric energy on the transmission line can be reduced
13. The principle of motor: the electrified coil rotates under the force in the magnetic field. It is the conversion of electric energy into mechanical energy
Principle of generator: electromagnetic induction phenomenon. Mechanical energy is converted into electric energy. Microphone and transformer use the principle of electromagnetic induction
15. Optical fiber is the medium for transmitting light
16. The magnetic induction line comes from the N pole of the magnet and finally returns to the S pole
Note: when there is voltage and electric power in the name plate, calculate r first, (r =). In addition, if there is "normal operation" in the title, it implies the condition

The formula of junior high school science

All the formulas of junior high school science
Common physical formulas and important knowledge points
1、 Physical formula
Deformation of unit formula and remark formula
Series circuit
Current I (a) I = I1 = I2 = The current is equal everywhere
Series circuit
Voltage U (V) u = U1 + U2 + Start of series circuit
Partial pressure action
Series circuit
Resistance R (Ω) r = R1 + R2 +
Parallel circuit
Current I (a) I = I1 + I2 + The main circuit current is equal to the current of each circuit
Sum of branch currents (shunt)
Parallel circuit
Voltage U (V) u = U1 = U2 =
Parallel circuit
Resistance R (Ω) = +
Ohm's law I=
Current and voltage in circuit
In direct proportion to the resistance
Current definition I=
Q: Charge quantity (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
Electromagnetic wave velocity and wave propagation
The relationship between length and frequency C = λ ν C:
Unit formula of physical quantity
Name symbol name symbol
Mass m kg m = PV
Temperature T ° C ° C
Velocity v m / S M / S v = s / T
Density p kg / M 3 kg / m3 P = m / V
Force (gravity) f Newton (cow) n g = mg
Pressure P Pascal PA P = f / S
Work w Joule (joule) J W = FS
Power P watt W P = w / T
Current I a (a) a i = u / R
Voltage U V U = IR
Resistance R ohm (Ω) r = u / I
Electric work w Joule (joule) J W = uit
Electric power P watt (watt) W P = w / T = UI
Heat Q Joule J Q = cm (T-T °)
Specific heat C coke / (kg ° C) J / (kg ° C)
The speed of light in vacuum is 3 × 108 M / s
G 9.8 N / kg
Sound speed 340m / s in air at 15 ° C
Junior high school physics formula compilation
[mechanics part]
1. Speed: v = s / T
2. Gravity: g = mg
3. Density: 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 = G-F (apparent gravity)
(3) , f floating = g (floating, floating)
(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 dynamic) / N (vertical direction)
11. Work: w = FS = GH
12. Power: P = w / T = FV
13. Principle of work: W hand = w machine
14. Actual machine: wtotal = w + W extra
15. Mechanical efficiency: η = w / W
16. Pulley block efficiency:
(1) , η = g / NF (vertical direction)
(2) , η = g / (G + G) (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. Efficiency of furnace and heat engine: 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 pressure 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）、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 quantities
1. Speed of light: C = 3 × 108m / S (in vacuum)
2. Sound speed: v = 340m / S (15 ℃)
3. Echo discrimination of human ear: ≥ 0.1s
4. Acceleration of gravity: g = 9.8n/kg ≈ 10N / kg
5. Standard atmospheric pressure value:
760 mm mercury column height = 1.01 × 105 pa
6. Water density: 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?℃)
10. Elementary charge: e = 1.6 × 10-19c
11. Voltage of one dry cell: 1.5V
12. Voltage of one lead-acid battery: 2V
13. Safety voltage for human body: ≤ 36V (not higher than 36V)
14. Power circuit voltage: 380V
15. Home circuit voltage: 220 V
16. Unit conversion:
（1）、1m/s＝3．6km/h
（2）、1g/cm3 ＝103kg/m3
（3）、1kw?h＝3．6×106J
Chemical reaction
1. Combustion of magnesium in air: 2mg + O2 ignites 2MgO
2. Combustion of iron in oxygen: 3Fe + 2O2 ignites Fe3O4
3. Combustion of aluminum in air: 4Al + 3O2 ignites 2al2o3
4. Combustion of hydrogen in air: 2h2 + O2 ignites 2H2O
5. Combustion of red phosphorus in air: 4P + 5o2 ignites 2p2o5
6. Sulfur powder burning in air: S + O2 ignites SO2
7. Full combustion of carbon in oxygen: C + O2 ignites CO2
8. Incomplete combustion of carbon in oxygen: 2C + O2 ignites 2CO
9. Carbon dioxide passing through hot carbon layer: C + CO2 high temperature 2CO
10. Combustion of carbon monoxide in oxygen: 2CO + O2 ignites 2co2
11. Reaction of carbon dioxide and water (carbon dioxide into purple litmus test solution): CO2 + H2O = = = H2CO3
12. Quicklime dissolved in water: Cao + H2O = = = Ca (OH) 2
13. Anhydrous copper sulfate as desiccant: CuSO4 + 5H2O = = = = CuSO4? 5H2O
14. Combustion of sodium in chlorine: 2Na + Cl2 ignites 2nacl
decomposition reaction
15. Preparation of oxygen from hydrogen peroxide in laboratory: 2h2o2, MnO2, 2H2O + O2 ↑
16. Heating potassium permanganate: 2kmno4 heating k2mno4 + MnO2 + O2 ↑
17. Under the action of direct current, water is electrified by 2H2O, 2h2 ↑ + O2 ↑
18. The carbonic acid is unstable and separated into H2CO3 = = = H2O + CO2 ↑
19. High temperature calcined limestone (carbon dioxide industrial process): CaCO3 high temperature CaO + CO2 ↑
Displacement reaction
20. Reaction of iron with copper sulfate solution: Fe + CuSO4 = = FeSO4 + Cu
21. Reaction of zinc with dilute sulfuric acid (hydrogen production in laboratory)