Q5.40 A thin circular loop of radius R rotates about its vertical diameter with an angular frequency . Show that a small bead on the wire loop remains at its lowermost point for . What is the angle made by the radius vector joining the centre to the bead with the vertically downward direction for ? Neglect friction.
The FBD of the loop is given below :
Using equilibrium conditions we can write :
and
Consider OPQ, we have :
or
Using l in above equation we get :
or
And
Thus
Since
Substituting the value of in the above equation:-
Thus
or