國的肌何质( Properties of Plane Areas)國□ §1-2极惯性矩、惯性矩、惯性积 (Polar moment of inertia, Moment of inertia, Product of inertia) 、惯性矩( Moment of inertia) dh Z dA VdA 二、极惯性矩( Polar moment of inertia) =Jpa4p2=x2+y2=「 dA 所以1P=12+1y(Properties of Plane Areas) §1-2 极惯性矩、惯性矩、惯性积 (Polar moment of inertia、Moment of inertia、Product of inertia) y z O dA y z  二、极惯性矩 (Polar moment of inertia） 一、惯性矩(Moment of inertia)   = = A z A y I y A I z A d d 2 2  = A IP dA 2  z y 2 2 2  = +  = A IP dA 2  所以 z y I = I + I P