Question
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 the figure. When a string is cut, the initial angular acceleration of the rod is,
-
3g / 2L
-
g/L
-
2g/L
-
2g/3L
Solution
A.
3g / 2L
Torque on the rod = moment of weight of the rod about P
... (i)
Moment of inertia of rod about,
... (ii)
As 
= I 
From equations (i) and (ii), we get
