For a rigid slab in plane motion, show that the system of the effective forces consists of...

For a rigid slab in plane motion, show that the system of the effective forces consists of vectors  attached to the various particles Pi of the slab, where  is the acceleration of the mass center G of the slab, ω is the angular velocity of the slab, α is its angular acceleration, and  denotes the position vector of the particle Pi, relative to G. Further show, by computing their sum and the sum of their moments about G, that the effective forces reduce to a vector  attached at G and a couple