To just complete the vertical circle around nail ‘P’ Mgr sin 30° =
1
2
m3g(l−r)
r = 3l - 3r r =
3l
4
The velocity of the ball when the string just touches the nail ‘P’ is V = √2glsin30° = √gl Tension in the string just after touching the nail ‘P’ is T - mg cos 60° =