Find the speed: v=s/t
Find the distance: s=vt
Discovery time: t=s/v
2. the speed formula of variable-speed linear motion: v = s/t.
3. The relationship between the weight and mass of an object: G=mg (g=9.8N/kg).
4. Definition of density
Find the density of matter: ρ = m/v.
Find the mass of matter: m = ρ v.
Find the volume of matter: V=m/ρ
4. Pressure calculation.
Definition: p=F/S (substances can be used in any state)
Liquid pressure: p=ρgh(h is depth)
Find the pressure: F=pS
Find the stress area: s = f/p.
5. Calculation of buoyancy
Weighing method: f floating = g-f
Formula: F float =G row = ρ row V row G
Float method: F float =G object (V row < V object).
Suspension method: F float =G object (V row =V object)
6. Lever balance condition: F 1L 1=F2L2.
7. definition of work: W=Fs
8. power definition: P=W/t
For uniform linear motion: P=Fv (F is a power)
9. Mechanical efficiency: η = useful power/total power
For lifting objects:
W useful =Gh(h is height)
W total =Fs
10, slope formula: FL=Gh.
1 1, heat absorption and heat release when the temperature of the object changes
Q suction = cm Δ t (Δ t = t-t0)
Q amplifier = cm δ t (δ t = t0-t)
12. Calculation of heat released by fuel combustion: Q =qm.
13, heat balance equation: q absorption =Q discharge.
14, heat engine efficiency: η=W useful /Q amplifier (q amplifier =qm)
15, current definition: I=Q/t (Q is electric quantity in coulomb).
16, ohm's law: I=U/R
Deformation voltage: U=IR
Deformation resistance: r = u/i.
17. Features of series circuit: (Take two pure resistance appliances in series as an example)
Voltage relation: U=U 1+U2
Relationship of current: I=I 1=I2.
Resistance relation: R=R 1+R2.
18. Features of parallel circuit: (Take two pure resistance appliances in parallel as an example)
Voltage relation: U=U 1=U2.
Relationship of current: I=I 1+I2.
Resistance relation:1/r =1/r1+1/R2.
19, electric work calculation: W=UIt.
20. the definition of electricity is p = w/t: p = w/t.
Common formula: P=UI
2 1, Joule's law: Q amplifier =I2Rt
For pure resistance circuit: Q amplifier = I2RT = U2T/R = UIT = Pt = UQ = W.
22. Calculation of total power of lighting circuit: P = P 1+P 1+ ...