A rod PQ of mass M and length L is hinged at end P. The rod is kept horizontal by a massless string tied to point Q as shown in figure. When string is cut, the intial angular acceleration of the rod is

A rod PQ of mass M and length L is hinged at end P. The rod is kept ho

1.	A rod PQ of mass M and length L is hinged at end P. The rod is kept horizontal by a massless string tied to point Q as shown in figure. When string is cut, the intial angular acceleration of the rod is
Answer» `(3g)/(2L)` `(G)/(L)` `(2G)/(L)` `(2g)/(3L)` Solution : Torque on the rod = Moment of weight of the rod about P, `tau = "Mg" (L)/(2)` ….(i) `because` Moment of INERTIA of rod about P, `I = (ML^(2))/(3)` ….(ii) As `tau = I alpha` From Eqs. (i) and (ii), we GET `"Mg"(L)/(2)=(ML^(2))/(3)alpha` `:.` The initial angular acceleration of the rod `alpha = (3g)/(2L)`