Kinematics Composite motions of a particle V=v+卫 aa=ae+a.( when the embroiling motion is translation a =a ta +a c when the embroiling motion is rotation where ak=2O×,=2o,si(a 2) Motion of a rigid body Translation( can be simplified to the motion of a particle) At any moment, the trajectories, velocities and accelerations at all points in the body are identical Rotation about a fixed axis p=f(t),@ do d o 8= 0=00+ E=const: uniformly accelerated rotation) 0=90+00t+ar2 ( when t=00=00,9=90) O2=002+2(-() 77 Composite motions of a particle a e r v = v + v aa = ae + ar （when the embroiling motion is translation） aa = ae + ar + ak （ when the embroiling motion is rotation ） where 2 , 2 sin( , ) k e r k e r e r a =  v a =  v  v Translation ( can be simplified to the motion of a particle） At any moment, the trajectories, velocities and accelerations at all points in the body are identical. Rotation about a fixed axis 2 2 ( ) , , dt d dt d dt d f t      =  = = = ＝const: (uniformly accelerated rotation)  = +t 0 2 0 0 2 1  = + t+ t 2 ( ) 0 2 0 2  = +   − (when 0 , ) =  =0  =0 t 2) Motion of a rigid body