james_hobson
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AS-Level Physics - Mechanics - OCR

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james_hobson
Created by james_hobson about 11 years ago
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Athishvelan Chettiar
Athishvelan Chettiar
over 8 years ago
nice
Lata To'a
Lata To'a
over 9 years ago
This is awesome! <3
christinahelenee
christinahelenee
over 10 years ago
This is totally brilliant and has helped me so much!! Thankyou!!!
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MechanicsVectors &ScalarsVectorsDisplacementVelocityAccelerationVectors have both magnitude and direction.The length of the line represents the magnitudeTwo vectors are only equal if they have the same magnitude and directionScalarsDistanceSpeedMassScalars have magnitude onlyThe rate of change of displacementRate of change of distanceMomentumMass x VelocityRate of change of velocityIf a body is moving in a circular path with a constant speed, the velocity is NOTconstant as the direction is changingDistance/timeSpeed = MAGNITUDE of velocity (in a straight line where distance=displacement)Magnitude of velocity = magnitude of displacement / timeInstantaneous Speed = Magnitude of instantaneous velocityAddition and Components of VectorsAdditionThe resultant of two or more vectors is the single vector that producesthe same effect (magnitude and direction).ComponentsParallelogram RuleA+B=RF can be resolved into two perpendicular vectorsMotionNewton's Laws1st LawEvery body continues at a state of rest or of uniform (unaccelerated) motion unless acted on by an external force2nd LawThe acceleration of a body is directly proportional to the external force acting on the body andtake place in the direction of the forceF=ma3rd LawIf A exerts a force on B, then B exerts and equal and opposite force on AThe Newton (N) is defined as the force to accelerate a mass of 1kg at 1m/s^2SUVATFor constant velocitys=vtFor constant accelerationv=u+atv^2=u^2+2ass=ut+½at^2s=½(u+v)tD-T GraphsGradient=velocityV-T GraphsGradient = AccelerationArea under graph = distanceConservation of momentumThe total linear momentum of a system of interacting (colliding) bodies, onwhich no external force is acting, remains constantIf two bodies A and B collide they exert qual and opposite forces on each other (Newton's 3rd Law),and by Newton's 2nd Law each body experiences the same acceleration. As the changes are oppositelydirected the total change in momentum is 0Elastic CollisionNo loss of kinetic energyTorque(Moments)M = FdM = Moment, F = magnitude of Force, d = perpendicular distanceCouplesTwo forces (equal in magnitude) which are antiparallel.Can only produce rotation, not translational motionMoment of couple = One force x separation of forcesEquilibrium, Centre of Mass andCOGConditions for equilibriumA body is in equilibrium if:Acceleration on COM is 0 in all directions and angular acceleration is 0The resultant force on COM is 0 and the total torque is 0A body may still be moving, but with constant velocity and aconstant angular velocity if rotatingTotal clockwise moment = Total anticlockwise moment (in equilibrium)Concurrent Forces = Forces where the lines ofaction meet at a single pointTriangle of ForcesPolygon of ForcesTypes of EquilibriumStableUnstableNeutralReturns to original position aftera slight displacementAfter displacement, it does not return to its originalposition or stay in its displaced positionA body stays in its displaced position afterbeing displaced slightlyCentre of MassThe MASS of an objectcan be considered toact at a single pointIn asymmetricaland uniformbody the COM isin the geometriccentreCentre of GravityA point where the WEIGHT of a body is considered to actCan be found by hanging the object with a plumb lineWork, Energy andPowerW=FdWork done = force x distance movedForce at angle to motionW = Fdcos(angle)Kinetic energy = ½mv^2GPE = mghTherefore, Increase/decrease in GPE = mg(change in h)Power = energy/timePower is the rate of doing work in WattsA pendulum converts GPE into KE and back to GPE, until it stopsas it loses energy in other forms (e.g. heat)Free FallGalileoDropped balls from the Leaning Tower of Piza to see acceleration during free fallHe discovered that objects fall at the same speed regardless of their massAristotleAristotle assumed that heavier objects would fall faster than lighter onesWeight = mass x acceleration in free fall (g)W = mgDensity = mass / volumePressure = force / areaCar SafetyStopping d = thinking d + braking dKE = braking force x braking distanceAffected by conditions, tyre tread etc.Safety featuresSeat beltsSeat belts are wide and soft, so produce less injury than hitting the windscreenCrumple zonesThe crumple zones increases the distance the force is acting, so insudden deceleration in a crash they decrease the force enough to savethe passengersAllows time for the airbag to inflateAirbagsA flexible nylon bag, an accelerometer detects the crashand starts a chemical reaction, producing nitrogen to fillthe airbagGPSTrilaterationA satellite sends out a signal and it arrives after a known time atthe GPS receiver then , given the speed of EM radiation, the distance ofthe receiver from the satellite can be found. The more satellites areused the more accurate the location is.Sankey DiagramsEnergy in = Energy outEfficiency(Useful output energy / total input energy) x 100%DeformationElasticReturns to original statePlasticPermanently deformedTensile (stretching) forceCompressive (squashing) forceHooke's LawF = kxWork done = ½kx^2E = ½Fx = ½kx^2After an object is stretched beyond its elastic limit it is plastically deformedYoung's ModulusStress = Force / AreaStrain = Extension / LengthYoung's Modulus = Stress / StrainDuctileDrawn into wiresBrittleDistort verylittleUltimate Tensile StrengthThe maximum amount of tensile force that can be applied to an object before it breaksUltimate Tensile StressThe maximum stress anobject can take before itbreaksDouble click this nodeto edit the textClick and drag this buttonto create a new node