F=r(⑦ In Cartesian coordinate system F =x(t)i +y(t)j+z(t)k In component form x =x(t) y=y() z=z(t)
r x t i y t j z t k ( ) ( ) ( ) r r(t) In Cartesian coordinate system In component form ( ) ( ) ( ) z z t y y t x x t x o z y r
△7=fB-F4=AB △F=△xi+△y+△xk Displacement Vector △=V△x2+△y2+2
r rB rA AB r xi yj zk 2 2 2 r x y z Displacement Vector
Velocity and Speed Velocity describe the rate of change of the position of the particle on its trajectory. Average Velocity:(平均速度) △F
Velocity and Speed Velocity describe the rate of change of the position of the particle on its trajectory. Average Velocity:（平均速度） m s t r v B A o z y x A r B r r
Instantaneous Velocity(瞬时速度)： 立=lim △F dr (ms） △t-→0 v=vi +V,j+vk dx dz dt b= d dt
v==V++图 Speed(速率) Average speed(平均速率) = △S ms） △t Instantaneous speed(即时速率) ds lim △t→0
2 2 2 x y z v v v v v Speed（速率） 1 m s t s v Average speed（平均速率） Instantaneous speed（即时速率） dt ds t s v t lim 0 s r B A