Recent results from a multiphase transport (AMPT) model [1] on the rapidity [2] and colliding system [3] dependence of the azimuthal anisotropies of particle momentum distributions in heavy ion collisions at the Relativistic Heavy Ion Collider will be reported. We find that while the observed transverse momentum dependence of the elliptic and 4-th order flows of charged hadrons at midrapidity can be described with the formation of a partonic matter during the early stage of the collisions, experimental data on the directed and elliptic flows of charged hadrons at large rapidity are better reproduced without the partonic matter. Also, both the elliptic flows of partons and charged hadrons scale linearly with the size of the colliding system. [1]Z. W. Lin, C. M. Ko, B. A. Li, B. Zhang, and S. Pal, nucl-th/0411110 and references therein. [2]L. W. Chen, V. Greco, C. M. Ko, and P. F. Kolb, Phys. Lett. B 605, 95 (2005). [3]L. W. Chen and C. M. Ko, nucl-th/0505044.