O Figure 1 Inertia experimental apparatus of rigid body The inertia experimental apparatus of rigid body is shown in Figure 1.Cone pulley A is a rotating object with five different radius(15、25、30、20、l0mm),with homogeneous thin rods B and B'with evenly divided scale at its two sides.Two movable cylindrical weights mo are located at B and B',respectively.They form together a rigid body system that can rotate around fixed axis OO'.There is a thin wire connected with the weight m.Different number of weights can be placed on the hook to change the torque applied on the rotating system. Principle: When a rigid body rotates around a fixed axis,according to the law of rotation, there is: M=JB (1) In which M is the total external torque being exerted on the rigid body,J is the moment of inertia of the rigid body to this axis,B is the angular acceleration In the apparatus,there are two external torques exerted on the rigid body system: One is the torque from the tension of the wire T,Mr=Tr,r is the radius of the reel on the cone pulley. Another is the friction torque at the bearings M2 Figure 1 Inertia experimental apparatus of rigid body The inertia experimental apparatus of rigid body is shown in Figure 1. Cone pulley A is a rotating object with five different radius (15、25、30、20、10mm), with homogeneous thin rods B and B′ with evenly divided scale at its two sides. Two movable cylindrical weights m0 are located at B and B′, respectively. They form together a rigid body system that can rotate around fixed axis OO′. There is a thin wire connected with the weight m. Different number of weights can be placed on the hook to change the torque applied on the rotating system. Principle: When a rigid body rotates around a fixed axis，according to the law of rotation, there is: M = J （1） In which M is the total external torque being exerted on the rigid body, J is the moment of inertia of the rigid body to this axis, β is the angular acceleration In the apparatus, there are two external torques exerted on the rigid body system: One is the torque from the tension of the wire T, MＴ=T r, r is the radius of the reel on the cone pulley. Another is the friction torque at the bearings Mμ. A B B′ m0 m0 m O′ O