A uniform rod  of mass 2 kg is hinged at one end .The rod is kept in the horizontal position by a massless string tied to point . Find the reaction of the hinge (in N) on end  of the rod at the instant when string is cut

(5)

When the string is cut, the weight of the rod constitutes torque about the hinge, so

(i)

According to Newton's second law,

     (ii)

Where  is the angular acceleration of the rod about the end . From Eqs. (i) and (ii), we get

Or 

Here , therefore

Acceleration of the CM of the rod is

Again by Newton’s second law,

Or