I was reading vertical circular motion, and found that the minimum velocity required to loop the loop is √5gl where l is the length of the string/radius of the vertical circle. However when I also read this
If the velocity given at lowest position v = √4gl,, the bob will be able to reach the highest point but the tension in the thread becomes zero before reaching the top position and afterward it will no longer be in circular motion. As soon as the thread will slack at an angle θ = cos^-1(-2/3) particle becomes free to move and it will follow the projectile path.
And after that , I saw some more illustrations:-
Now I am not able to understand where do I consider the minimum initial velocity as √5gl or √4gl for reaching the maximum position... Basically could anyone just explain me this:-
"even if normal is zero , the bead will not lose contact with the track, normal can act radially outward"