2. Physics quantities to describe the particle motion 2.1 Position Vector, Displacement and Motional Equation 1)position vectors r=OP=0A+ AB+ Bp aP(x,y, r=xi+ vi+zk Magnitude is determined by: r+ytz Direction is determined by: x cosa=x/r; cos B=y/r; cosy=z/r cos a+coS B+cos y=12. Physics quantities to describe the particle motion 2.1 Position Vector , Displacement and Motional Equation 1) position vectors r xi yj zk ˆ ˆ ˆ = + +  cos cos cos 1 cos / ;cos / ;cos / 2 2 2 + + = = = =     x r  y r  z r Direction is determined by: 2 2 2 r = r = x + y + z  Magnitude is determined by: → r = OP  → → → = OA+ AB+ BP o x y z •P(x,y,z) x y z    A B C r