And how to apply all the formulas!

And how to apply all the formulas!

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: 9.8n/kg or 10N / kg
Density ρ (kg / m3) ρ = m / V M: mass V: Volume
The direction of resultant force F (n) is the same: 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
Unit) formula remarks formula deformation
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 # 179; kg / m # 179; 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
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Junior high school physics formula and unit

Physical quantity unit formula name symbol name symbol mass m kg kg m = PV temperature T centigrade ° C velocity v m / S v = s / T density p k

Who knows the symbol of physical electricity?
The more complete the better!

1、 Electrical symbols of physical quantities
1. Charge quantity: Q, unit: C,
2. Elementary charge: e; 1E = e = 1.60218 × 10 ^ - 19C & nbsp;
3. Current: I, unit: a
4. Voltage: u, & nbsp; & nbsp; unit: v
5. Resistance: R, & nbsp; & nbsp; unit: Ω
6. Electric work: W, unit: J
7. Electric power: P, unit: W
2、 The common electrical symbols in the circuit diagram are as follows:

All junior high school physics formula (Optics, electricity, mechanics) thank you
Translate any letters into Chinese

Junior high school physics formula physical quantity (unit) formula remarks formula deformation gravity g = mg m: mass G: 9.8n/kg or 10N / kg density ρ = m / V M: mass V: Volume resultant force F combination direction is the same: F combination = F1 + F2 direction is opposite: F combination = f