This paper analyzes the fundamental dynamic motion of a robotic arm and body mechanism on the platform of a mobile manipulation system. For the purpose, we reveal the dynamic coefficients of a robotic arm and body mechanism, and identify their dominant behaviors in an exemplar trajectory following simulation. We also discuss on their influence for the motion of the body, shoulder, and elbow joints. It is finally expected that this analysis is helpful for effective manipulation tasks by using mobile manipulation systems with an arm and body mechanism.