初一、初二、初三物理知识总结（Summary of physics knowledge first, second and third）.docVIP

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初一、初二、初三物理知识总结（Summary of physics knowledge first, second and third）.doc

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初一、初二、初三物理知识总结（Summary of physics knowledge first, second and third）

初一、初二、初三物理知识总结（Summary of physics knowledge first, second and third） Division of force division Speed: V = S/t 2. Gravity: G = mg 3. Density: rho = m/V 4. Pressure: p = F/S 5. Liquid pressure: p = rho gh 6. Buoyancy: (1) F float = F -f (pressure difference) (2) F float = g-f (apparent gravity) (3) F float = G (floating, suspension) (4) Archimedes principle: F float = G row = rho liquid gV row 7. Leverage balance condition: F1 L1 = F2 L2 8. Ideal inclined plane: F/G = h/L 9. Ideal pulley: F = G/n 10. Actual pulley: F = (G + G movement)/n (vertical direction) 11. Work: W = FS = Gh 12. Power: P = W/t = FV 13. Principle of work: W hand = W machine 14. Actual machinery: W is always equal to W plus W extra 15. Mechanical efficiency: eta = W has/W total 16. Efficiency of pulley block: (1) eta = G/nF (vertical) (2) eta = G/(G + G) (vertical direction excluding friction) (3) eta = f/nF (horizontal) [thermal division] : 1, absorption of Q = Cm absorption (t - t0) = Cm Δ t 2, exothermic: Q = Cm (t0) = Cm Δ t 3. Heat value: q = q/m 4. Efficiency of furnace and heat engine: eta = Q effective utilization of/Q fuel 5. Thermal equilibrium equation: Q = Q suction 6, thermodynamic temperature: T = T + 273K [electricity division] 1. Current strength: I = Q power/t 2. Resistance: R = rho L/S 3. Ohms law: I = U/R Joules law: (1) Q = I2Rt universal formula) (2), Q = UIt = Pt = UQ power = 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 over P2 = R1 over 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 over P2 = R2 / R1 7 fixed value resistance: (1) I1 / I2 = U1 / U2 (2) P1 / P2 = I12 / I22 (3) P1 / P2 = U12 / U22 8 electrical work: (1) W = UQ = UQ (universal formula) (2) W = I2Rt = U2t/R (pure resistance formula) 9 power: (1), P = W/t = UI (universal formula) (2), P = I2R = U2