Two particles, each with mass m = 5.4 g, are fastened to each other and to a rotation axis at P, by two thin rods, each with length L = 0.68 m and each with a mass of 7.9 g, as shown. The combination rotates around the rotation axis with an angular velocity of 10.4 rad/s. Find the rotational inertia (i.e. the "moment of inertia") of the combination about P. The diagram is like this... p------o------o p being the pivot and the o's being the masses. Rotational Inertia = The sum of all... mi+ri^2 There's also The sum of all .. 1/2mi(wri)^2 = 1/2(The sum of all .. miri^2)w^2. Sorry i don't really know how to write out the formulas hehe. I don't understand how to add the sums of the masses*radius^2. like where do you start and stop? Do you just add up the lenth after the pivot and add up the mass of that and plus those into the first equation? Any help would be awesome.