IB›IB Physics HL›Mind mapsA.2 Forces and momentumIB Physics HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsNewton's lawsFirst: constant velocity unless resultant force actsSecond: F=ΔpΔtF = \frac{\Delta p}{\Delta t}F=ΔtΔp, or F=maF = maF=ma for constant massThird: equal and opposite, on different bodiesThird law pair are the same type of forceContact forcesNormal force is perpendicular to the surfaceStatic friction: Ff≤μsFNF_f \le \mu_s F_NFf≤μsFNDynamic friction: Ff=μdFNF_f = \mu_d F_NFf=μdFNHooke's law: FH=−kxF_H = -kxFH=−kxDrag on a sphere: Fd=6πηrvF_d = 6\pi\eta r vFd=6πηrvBuoyancy: Fb=ρVgF_b = \rho V gFb=ρVgField forcesGravitational force (weight): Fg=mgF_g = mgFg=mgElectric force acts between chargesMagnetic force acts on moving chargesAct without contactForcesand momentumFpJNMomentump=mvp = mvp=mv, a vectorConserved if no resultant external forceImpulse J=FΔt=ΔpJ = F\Delta t = \Delta pJ=FΔt=ΔpLonger contact time means smaller average forceCollisionsElastic: kinetic energy conservedInelastic: some kinetic energy transferred awayExplosion from rest: equal and opposite momentaLighter fragment gets the larger speedExam tipsWeight and normal force are not a third law pairTerminal speed: weight = buoyancy + dragMomentum is conserved in inelastic collisions tooNever draw centripetal force as an extra force