Rigid rods of negligible mass lying along the y axis connect three particles (Fig. P10.20). The system rotates about the x axis with an angular speed of 1.20 rad/s. (a) Find the moment of inertia about the x axis. So isnt the moment of inertia given by the sum of mr so.. (4kg)(3m)+(2kg)(-2m)+(3kg)(-4m) = -4?