when an object, say, a remotely retractable rod is revolving about a fixed axis on a frictionless ice ( so Fn=mg are all the forces act on it )
if i press the button to remotely retract the rod from lenght l to lenght l1 (l1< l). Then momenta should be Iw = I1w1 where I1w.
the only force acting could only be the force to pull the rod inward which is directed towards the axis, hence, has zero torque is acting on the system
if there is zero torque, we got Σtorque = Iα = 0, hence, α=0
if angular acceleration = 0 then how could w change?