PROBLEM 9.129 Shown is the cross section of a molded flat-belt pulley. Determine its mass moment of inertia and its radius of gyration with respect to the axis .AA′(The specific weight of brass is 0.306 lb/in3and the specific weight of the fiber-reinforced polycarbonate used is 0.0433 lb/in3.) SOLUTION First note for the cylindrical ring shown that ()22214mVtddπρρ==×−and, using Figure 9.28, that 1122AAImm′=−1844tdddππ=×−×441td dρ21211td d d d+( )1218mdd=+Now treat the pulley as four concentric rings and, working from the brass outward, have ()()320.306lb/in0.875 in.0.55 in.0.25 in.
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