nstantaneous velocity(瞬时速度) △ △M>0△tat x()+y(1)j+z( =vr+yuj+v,k=v(t) Instantaneous Acceleration Aνdνddr)d a=lim △→0△ t dtdt dt)dtInstantaneous velocity (瞬时速度) : x t i y t j z t k  dt d dt dr t r v t       ( ) ( ) ( ) lim 0 = + + =   =  → v i v j v k v(t) x y z     = + + = InstantaneousAcceleration: 2 2 0 d d d d d d d d lim t r t r t t v t v a t       =      = =   =  →