A weightless thread can bear tension upto 3.7 kg wt. A stone of mass 500 gm is tied to it and revolved in a circular path of radius 4m in a vertical plane. If g=10 ms−2 , then the maximum angular velocity of the stone will be :-
(1) 16 rad/s
(2) 21 rad/s
(3) 2 rad/s
(4) 4 rad/s