A plank AB of length l is gently released on a knife edge at 0 as shown in the figure. If AOis made l4, the angular acceleration of the plank just after it is released is

Mass of segment AO, m1=m4Mass of segment BO, m2=3m4M = Net moment about O=3mg4×3l8−mg4×l8=14 mglI0=13(m4)(l4)2+13(3m4)(3l4)2=748ml2∴ Angular acceleration, α=MI0=14mgl748ml2=127 gl