Here, A,B are strings. A was cut. The rod is of length l. Acceleration of center of mass = a and angular acceleration of the rod is alpha.
Now if I want to find the net torque about the point of intersection of B and the rod(which is accelerating towards the right with $l/2 sin37 \theta $), why do I have to apply a pseudo force on the c.o.m and observe it from that accelerating frame to equate net torque = $I\alpha$ (including the torque due to pseudo force)? Why can't we do it from the ground frame? why does the point about which we take the net torque and equate it to $I\alpha$ have to be non-accelerating?