Hi, I have to find examples,application about points which represent a rigid body.In the lecture dynamics of machines we call them substantial points. the points have a mass which is equal to rigid body for example a mechanism. to do this we use kinetic energy equalities. 1/2(ma*va2)=([itex]\sum(Ek)[/itex])i and 1/2 (ma *va^2)=∑(1/2 mi*vi^2 + 1/2*Ii*wi^2) these two are the formulas: ma:(induced,reduced?) point A, mi: mass of the İth body(in the ∑ symbol), vi is the velocity of center of mass of the İth body, Ii is the moment of inertia of the ith body and wi is the angular velocity of the ith body. we also study (reduced?) moment of inertia of the machine( for example a fourbar mechanism) to a mile(or axle). here is the formula 1/2*I*w^2=∑1/2*mp*vp^2 here: I is the moment of inertia student has to find which represents I think all the kinetic energy mp is the mass of pth body of the machine(or mechanism) I want to make a google search about this but I dont know true words for this subject. Can you help me. And have ever met this subject in the books about dynamics of machines I have never met with them in english books. at least reduced( or equivalent) momet of inertia part.