a=(r-ro)i+(rot2r0)j a,i+80 2 a,=r-rA =r+2r-10) ●● r di 注意: dr ●● 虽然 Vr= 但 a,≠ dt 12 a r r i r r jˆ ( 2 ) ˆ ( )2 •• • •• • • = − + + ar iˆ a jˆ = + = + = −• • • • • • • a r r ar r r 2 2 ( ) 1 2 • = r dt d r 注意: 虽然 dt dr v r = 但 • • ar r 12