The cinematics of progressive movement. Speed and move point
The solid body, the non-deformable body, is such that in any movement and interaction the distance between any two points of this body remains the same. The progressive movement of the solid is a movement in which the segment connecting any two points of the body is transferred parallel to itself. When moving forward, the trajectory of all points of the body is the same, so it is enough to consider the movement of any point of the body, such as the center of the masses. If such a point is attributed to the entire body weight, then it is called a material point.