Complete collection of junior high school physics formulas

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=ρgh

6. Buoyancy:

(1) F float = F'-F (pressure difference)

(2) F float = G-F (depending on gravity)

(3) F float =G (floating, suspended)

(4) Archimedes' principle: F float = G row = ρ liquid gV row

7. Lever balance conditions: F1 L1＝F2 L2

8. Ideal slope: F/G＝h/L

9. Ideal pulley: F=G/n

10. Actual pulley: F =(G+G motion)/ n (vertical direction)

11. Work: W＝FS＝Gh (lifting the object high)

12. Power: P＝W/t =FV

13. The principle of work: W hand = W machine

14. Actual machinery: W total = W has + W extra

15. Mechanical efficiency : η＝Whas/Wtotal

16. Pulley block efficiency:

(1) η＝G/nF (vertical direction)

(2) η＝G/(G＋G motion) (excluding friction in the vertical direction)

(3) η＝f / nF (horizontal direction)

Thermal part

1. Endothermic: Q absorb = Cm (t-t0) = CmΔt

2. Heat release: Q release = Cm (t0-t) = CmΔt

3. Calorific value : q=Q/m

4. Efficiency of furnaces and heat engines: eta=w/Q fuel

5. Heat balance equation: Q release = Q absorb

< p>6. Thermodynamic temperature: T＝t+273K

Electrical part

1. Current intensity: I＝Q power/t

2. Resistance: R= ρL/S

3. Ohm’s law: I=U/R

4. Joule’s law:

(1) Q=I?2Rt universal formula )

(2) Q＝UIt＝Pt＝UQ electric quantity＝U?2t/R (pure resistance formula)

5. Series circuit:

（ 1) I＝I1＝I2

（2）U＝U1＋U2

（3）R＝R1＋R2

（4）U1/U2＝R1/R2 (Voltage dividing 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 fixed value resistor:

(1) I1/I2＝U1/U2

（2）P1/P2＝I12/I22

（3）P1/P2＝U12/U22

8 power Work:

(1) W＝UIt＝Pt＝UQ (universal formula)

(2) W＝I?2Rt＝U?2t/R (pure resistance formula)

9 Electric power:

(1) P＝W/t＝UI (universal formula)

(2) P＝I?2R＝U? 2/R (pure resistance formula)

10. Electromagnetic wave: c=λf