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物理復習

2023-06-05 13:29 作者:鉛灰線  | 我要投稿

Chapter1 kinematics

1.displacement:Δx=x-x0

2.speed-velocity

1speed=d/t

2v=dx/dt

3.acceleration

1a=dv/dt

2constant acceleration

x=x0+1/2v+v0t=x0+v0t+1/2 at*2

v=v0+at

v*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

1Fn is the reading of the scale, and mg is actually the weight.

2when the a0,Fnmg,overweight,and weightless the opposite

4 static and kinetic frictional force

1fsfsmax=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(動能)

1Ek=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(重力勢能)

Wg=mg(h0-hf)=-mgΔh

Epg=mgΔh

4 elastic potential energy(彈性勢能)

Eptension=1/2k(Δx*2

5 mechanical energy

(1)Emc=Ek+Ep

(2)Wnc=ΔEk+ΔEp

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

compare 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 impulseJ=(ΣF)Δt

2momentump=mv

3(ΣF)Δt=mvf-v0

1the change of momentum can be calculated by impulse

2if the net external force is zero,the momentum will be constant

4collision

1elastic one:ΔEk=0but momentum remains the same

(2)inelastic one:ΔEk0 ,and stick together while completely inelastic

5center

1Xcm=Σ(i=1nmixi/Σ(i=1,nmi

2Vcm=Σ(i=1nmivi/Σ(i=1,nmi

?

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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

1ac=v*2/r=rω*2directionto the center

2aT=rα=r dω/dt,direction tangential(切向)

5. =Fxr=Iα

1||=|F||r|sinθ

2positive direction counter clockwise

6.I

(1) one point:I=mr*2

2x pointsI=Σmiri*2

3ring

I=mr*2


4rod

I=1/3mL*2

I=1/12mL*2

5plate roundI=1/2Mr*2

6ballI=2/5mR*2

7I=Ic+md*2

ball on the ground:(1+2/5mR*2

ring(實心):(1+1/2mR*2

?

7.W=┏θ

8.Ek=1/2Iω*2

9.Langular momentum,角動量)=Iω

?

?

Chapter 6 Simple Harmonic Motion,elasticity

ideal springF=-kx

1.x=Acosωt,ω=2Πf=2Π(T*-1

2.v=Aωcosωt, a=Aω*2 cosωt

3.F=kx=max

1-kAcosωt=-mAω*2cosωt

(2) ω=(k/m)*0.5

4.energy: Ep=1/2kx*2

model 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

3combine together:ω=mgL/I*0.5

two other models

1.F=Y(ΔL/L0A

2.F=S(Δx/L0A


Chapter7 fluid

1.Δp=ρhg,F=ρgV

2.pascals principleF proportional to Area

1F1/F2=S1/S2

2A1h1=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=5/9Tf-32),T=Tc+273.15

2.liner thermal expansion(熱脹冷縮)

1)ΔL=αL0ΔT

2)ΔV=βL0ΔT

3.Q

(1)Q=cmΔT

2Q=mLit means that if watersolid,0 turns into liquid0how much heat it needs

4.three ways of heat transference

1convection(對流)Q=kAΔTt/L

2conduction(熱傳遞)Q=cmΔT=mL

3radiation(輻射)Q= ξeAtT*4,其中ξ=5.67x10*-8J/sm*2K*4

?

Chapter9 waves and sound

1 conception

(1)A, λ,T,f

2f=1/T,v=λ/T=λf

2 speed of soundv=(γkT/m*0.5

3 sound intensityI

(1)I=P/A

(2)in a sphereA=4Πr*2

3)①Io=10*-12 W/m*2

I=1 W/m*2

4dB:β=10lnI/Io),Io=10*-12 W/m*2

4 doppler effect

fo=fsv±vo/v-+vs

1upperif observer moves to source,+

2lower if source moves to observer,-

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