For Balance (#11 on the IB): how exactly is the torque of the main rod calculated with regard to weights on attached rods (i.e. the two bottom rods on the main example)? When I first read the instructions, I thought each subordinate rod's torque on the main rod was calculated by adding the torque of both sides of the smaller rod and multiplying it by the distance of that rod's fulcrum to the main rod's fulcrum, but the math only balances out if you instead use each weight's horizontal distance to the main fulcrum without regard to vertical distance: with the former you get 2*5 _PLUS_ 1(2*2_PLUS_1*4) =! 4(3*1_PLUS_1*3), while with the latter you get 2*5_PLUS_3*2_PLUS_0*4=1*1_PLUS_5*3.