1. The problem statement, all variables and given/known data A uniform beam of mass mb and length supports blocks with masses m1 and m2 at two positions, as in Fig. P12.3. The beam rests on two knife edges. For what value of x will the beam be balanced at P such that the normal force at O is zero? 2. Relevant equations sum of F = 0 sum of moments = 0 3. The attempt at a solution I'm quite unsure regarding the forces to be drawn in my free body diagram. Example, the two normal forces by beam on the each masses. Do i draw them out? And at points P and O, is there a horizontal reaction force? How do i determine the forces at point P? Like when i looking at point P, do i think as the way below? (treat the knife edge at O as not existing) the beam can rotate at P, so no moments. but the beam cannot translate horiz and vert at P, so there are horiz and vert reaction forces. or I cannot treat the knife edge at O as not existing? If so, means the beam cannot rotate at P and there will be a moments? Do you all know what i mean? =x Can explain to me? Thanks!!