7-1 The motion of a complex object When we projectile a rigid body, the motion of the body looks very complicated We can consider the motion of the rigid body to be a combination of a parabolic trajectory of a"center of mass"(rotational motion is not considered) plus a rotation about center of mass"(translational motion is not considered) How to find the center of mass (CM) of a particle system?7-1 The motion of a complex object When we projectile a rigid body, the motion of the body looks very complicated. We can consider the motion of the rigid body to be a combination of a parabolic trajectory of a “center of mass” (rotational motion is not considered) plus a rotation about “center of mass” (translational motion is not considered). How to find the center of mass (CM) of a particle system?