8.1 The concept of absolute motion relative motioninvolving motionA bridge crane on the factory floor
A bridge crane on the factory floor 8.1 The concept of absolute motion relative motion involving motion
8.1 The concept of absolute motion relative motioninvolvingmotionyx'4Weight A-→A'A1The motion trajectory of point A:V1AAl curve movement - absoluteV1motion - ground observerAStraight up - relative motion0XMotion of the dynamic system:Horizontal translation - implicated motion
A A' Weight A→A' 0 x y 0' x' y' A1 v v1 v1 The motion trajectory of point A: ①AA1 curve movement - absolute motion - ground observer ②Straight up - relative motion 8.1 The concept of absolute motion relative motion involving motion Motion of the dynamic system: Horizontal translation - implicated motion
8.1 The concept of absolute motion relative motioninvolving motion3.Three speeds, three accelerationsAbsolutevelocity and acceleration:The velocity and accelerationofthe moving point relative to the static systemare expressed asv.aaRelative velocity and accelerationThe velocity and acceleration of the moving point relative to the movingsystem are expressed as v,a,Associated velocity and acceleration:Thevelocity and accelerationoftheimplicated pointrelative tothe staticsystem are expressed as ve ae①Atransient②Apoint onadynamic systemThe coincides with the movingpoint
3. Three speeds, three accelerations Absolute velocity and acceleration: ➢ The velocity and acceleration of the moving point relative to the static system are expressed as Relative velocity and acceleration: The velocity and acceleration of the moving point relative to the moving system are expressed as Associated velocity and acceleration: The velocity and acceleration of the implicated point relative to the static system are expressed as 8.1 The concept of absolute motion relative motion involving motion ①A transient ②A point on a dynamic system ③The coincides with the moving pointr v ar a v a a ve ae
8.1 The concept of absolute motion relative motioninvolving motionmovingrelativeabsolutepointvarv.a.(Point)(Point)absoluterelativemotionmotionStaticDynamic<translationalmotionsystemsystem(rigid)Atan instant,theinvolvepointon thev.atransportdynamicsystempointcoincideswiththemoving point
translational motion Static system Dynamic system moving point （rigid） absolute a v r v relative e v transport point involve a a r a e a 8.1 The concept of absolute motion relative motion involving motion At an instant, the point on the dynamic system coincides with the moving point
8.1 The concept of absolute motion relative motioninvolving motion Example1: CAM jacking mechanismMoving point: Point A on rod AB12Dynamic fastening: To fix to the CAMabsolutemotion:vertical curve公relative motion:An arc alongthe rimtransportmotion:The level of translationtransportpoint:A pointon the CAM thatcoincideswithA
Example1：CAM jacking mechanism 8.1 The concept of absolute motion relative motion involving motion 0 v A B O Moving point: Point A on rod AB Dynamic fastening: To fix to the CAM x y x’ y’ absolute motion: relative motion: transport motion: transport point: vertical curve An arc along the rim The level of translation A point on the CAM that coincides with A e v r v a v