物理复习
Chapter1 kinematics
1.displacement：Δx=x-x0
2.speed-velocity
（1）speed=d/t
（2）v=dx/dt
3.acceleration
（1）a=dv/dt
（2）constant acceleration
①x=x0+1/2（v+v0）t=x0+v0t+1/2 at*2
②v=v0+at
③v*2-v0*2=2aΔx
Chapter2 dynamics
1ΣF=ma,ΣF means net external force
N=kg m s*（-2）
2 gravitational force
F=GMm r*（-2），GM=gR*2
3 overweight weightless
Fn(support force)=mg+ma
（1）Fn is the reading of the scale, and mg is actually the weight.
（2）when the a＞0，Fn＞mg，overweight，and weightless the opposite
4 static and kinetic frictional force
（1）fs≤fs（max）=μsFn (actually the maximum of static frictional force is larger than constant kinetic frictional force )
Chapter 3 Work and energy
1 W=Fs=|F||S|cosα
2 kinetic energy（动能）
（1）Ek=1/2 mv*2
(2) the work done by net external force equal to the change of the kinetic energy:
W=Ekf-Ek0
3 gravitational potential energy(重力势能)
Wg=mg(h0-hf)=-mgΔh
Ep（g）=mgΔh
4 elastic potential energy（弹性势能）
Ep（tension）=1/2k（Δx）*2
5 mechanical energy
(1)Emc=Ek+Ep
(2)Wnc=ΔEk+ΔEp
① the force external to the system leads to the change of the mechanical energy, and calculate by the change of kinetic energy and the potential energy. That is to say, we can use the mechanical energy to solve the problem in a system
②compare to the constancy in mechanical energy， theorem of kinetic energy is to solve the problem in an object. For instance, if you work out the net force on an object and the relative distance, you can calculate the total work and thus know the change of the kinetic energy.
6 Power（功率）
P=W/t
Chapter 4 Impulse and momentum
1 impulse：J=（ΣF）Δt
2momentum：p=mv
3（ΣF）Δt=m（vf-v0）
（1）the change of momentum can be calculated by impulse
（2）if the net external force is zero，the momentum will be constant
4collision
（1）elastic one：ΔEk=0，but momentum remains the same
(2)inelastic one:ΔEk≠0 ，and stick together while completely inelastic
5center
（1）Xcm=Σ（i=1，n）mixi/Σ（i=1，n）mi
（2）Vcm=Σ（i=1，n）mivi/Σ（i=1，n）mi
Chapter 5 uniform circular motion
1translational to rotational
(1) x=x0+v0t+1/2at*2，θ=θ0+ω0t+1/2αt*2；x=rθ
(2)v，ω；v=rω
(3)a=dx/dt，α（角加速度）=dθ/dt
(4)v=v0+at，ω=ω0+αt，v=rω
(5)m,I=mr*2
(6)F=ma, ┏=Fxr，
(7)Ek=1/2mv*2,Ek’=1/2Iw*2
(8)W=Fx=┏θ
(9)dim clockwise as negative direction
2.θ=Δv/v=vΔt/r---Δv/Δt=v*2/r=ac
3.v=2Πr/T=rω
4.acceleration
（1）ac=v*2/r=rω*2，direction：to the center
（2）aT=rα=r dω/dt，direction： tangential（切向）
5. ┏=Fxr=Iα
（1）|┏|=|F||r|sinθ
（2）positive direction： counter clockwise
6.I
(1) one point:I=mr*2
（2）x points：I=Σmiri*2
（3）ring：
①I=mr*2
②
（4）rod
①I=1/3mL*2
②I=1/12mL*2
（5）plate round：I=1/2Mr*2
（6）ball：I=2/5mR*2
（7）I=Ic+md*2
①ball on the ground：（1+2/5）mR*2
②ring（实心）：（1+1/2）mR*2
7.W=┏θ
8.Ek=1/2Iω*2
9.L（angular momentum，角动量）=Iω
Chapter 6 Simple Harmonic Motion,elasticity
Ⅰideal spring：F=-kx
1.x=Acosωt，ω=2Πf=2Π（T*-1）
2.v=Aωcosωt, a=Aω*2 cosωt
3.F=kx=ma（x）
（1）-kAcosωt=-mAω*2cosωt
(2) ω=(k/m)*0.5
4.energy: Ep=1/2kx*2
Ⅱmodel of pendulum
1.（1）Σ┏=Fx=-mgLsinθ=-mgLθ
（2）θ=Acos cosωt/L
（3）Σ┏=-mgLcosωt
2.（1） Σ┏=Iα
（2）α=a/L=-ω*2Acosωt/L
（3）combine together：ω=（mgL/I）*0.5
Ⅲtwo other models
1.F=Y（ΔL/L0）A
2.F=S（Δx/L0）A
Chapter7 fluid
1.Δp=ρhg，F=ρgV
2.pascal‘s principle（F proportional to Area）
（1）F1/F2=S1/S2
（2）A1h1=A2h2
3.continuity（流量）
Δm=ρV=ρAvΔt
(1)Δm/Δt=ρVA
(2)ΔV/Δt=Q=Av
4.equation of Bernoulli
P1+1/2ρv1*2+ρgy1= P2+1/2ρv2*2+ρgy2
Chapter8 Temperature and heat
1.Tc=5/9（Tf-32），T=Tc+273.15
2.liner thermal expansion（热胀冷缩）
（1）ΔL=αL0ΔT
（2）ΔV=βL0ΔT
3.Q
(1)Q=cmΔT
（2）Q=mL（it means that if water（solid，0） turns into liquid，0，how much heat it needs
4.three ways of heat transference
（1）convection（对流）Q=kAΔTt/L
（2）conduction（热传递）Q=cmΔT=mL
（3）radiation（辐射）Q= ξeAtT*4，其中ξ=5.67x10*（-8）J/（sm*2K*4）
Chapter9 waves and sound
1 conception
(1)A, λ，T，f
（2）f=1/T，v=λ/T=λf
2 speed of sound：v=（γkT/m）*0.5
3 sound intensity：I
(1)I=P/A
(2)in a sphere：A=4Πr*2
（3）①Io=10*-12 W/m*2
②I=1 W/m*2
（4）dB：β=10ln（I/Io），Io=10*-12 W/m*2
4 doppler effect
fo=fs（v±vo）/（v-+vs）
（1）upper：if observer moves to source，+
（2）lower： if source moves to observer，-
