SAT物理常用公式

Vector and Forces

torque=forcelength of moment armthe sum of the clockwise moments=the sum of the counterclockwise momentsMotion and Forces

distance coveredtime requireddisplacementaverage velocity=timedistance covered=average speedtimeS=vavtaverage speed=acceleration=avfvichange in velocitytime required for changevttMotion with constant acceleration (starting from rest)vavvf/2vfat(vfgt)Svf2121at(Sgt2)222as(vf22gs)vavaverage speedvffinal velocityaaccelerationtelapsed timesdistance coveredvvfvavi2vfviat1Svitat22vf2vi22asFtchange in momentum=masschange in velocitymomentum=massvelocityCentripetal Force

v2acrmv2Fcr2rvT42ra2TGravitational FieldsGm1m2Fr2GMsvrWork, Energy, Simple Machines

distance  forceworkgravitational potential energy=mgh1kinetic energy=mv22force of friction during motionnormalwork against friction=frictiondistance object moves1elastic potential energy=kx22workpowertimeforcedistancepowertimecoefficient of sliding friction=change in length=oringinal lengthcoeff. of expansiontemp. change p1V1p2V2V=volume, T=absolute temperature, P=pressurep1V1p2V2T1T2Measurement of Heat

heat required for melting=massHFV1T1V2T2heat required for vaporization=massHVheat gianed(or lost)=masssp.ht.temp.change+mass meltedheat of fusion+mass vaporizedheat of vaporizationHeat and Work; Heat Transfer

heat flow=change ininternal energy+work done by systemQ=U+WWave Motion and Sound

Periodic MotionFor a stretched spring:FkxmT2kFor waves:1Tfvf (=wavelength)the number of beats=the difference between the two frequenceClosed Pipes=4laVibrating Air ColumnsOpen Pipes=2la=2lsGeometrical Optics: Reflection and Refraction

For a special mirror the focal length is equal to one-half of the radius of thespherical shellfR/2Law of Refractionsin1n(nindex of refraction)sin2nspeed of light in vacuum(or air)speed of light in the substancen2sin1n1sin2Images Formed by Lenses111object distanceimage distancefocal length111di dofsize of imageimage distancemagnification(m)size of objectobject distanceOBJECT DISTANCE Convex Lens(or Concave Mirror) greater than 2f 2f between f and 2f less than f Concave Lens(or Convex Mirror) any distance IMAGE CHARACTERISTICS real, smaller, between f and 2f, inverted real, same size, 2f, inverted real, larger, greater than 2f, inverted virtual. ;larger, q more than p, erect virtual smaller, erect, q less than p focal length of the objectivefocal length of the eyepieceintensity of sourceillminationdistance2telescopic magnification=Physical Optics: Interference and Diffraction

xdLwavelengthd=distance between the two siltsL=distance between the barrier and the screenx=distance between the central maximum and the first bright fringeStatic Electricity—Electric Circuits

kq1q2r2EF/q (E=electric field intensity,F=the force exerted on positive charge q)workpotential difference=chargeworkVqEV/d (E=electric field intensity,V=the difference of potential between the plates)workVqFLlength in metersρLR=resistance in ohmsRAA=cross-sectional area in meter2ρ=a constant for the material and is called resistivity; unit is ohm-meter /RTITVTRTVT/ITVTITRTseries circuit current resistance ITI1I2parallel circuit ITI1I2series-parallel circuit ITI3I1I2RTR3R1R2R1R2RTR1R2111RTR1R2VTV1V2voltage IR-drop symbols VTV1V2VTV1V3V2V3;V1V2VTITRT;V1I1R1;V2I2R2,etcI1current through R1;V2potential difference across R, etc.VTemfIrPVI;PI2R;PV2/RenergypowertimeMagnetism; Meters, Motors, Generators

FILB (Lthe length of wire in the magnetic field, B=the flux desity)FqvB (v=velocity)Elements of Electronics Capacitors and Capacitance Q=CV

1farad106microfarads1potential energy=CV22111Q22P.E.CVQV222CPhotons, Atoms, Nuclei

EkhfWEkkinetic energymomentum of the photon=Planck's constantwavelengthphhmvEmc2LL01(v2/c2)Special Relativity

tmt01(v2/c2)m01(v2/c2)