A ball weight 1.0 kg is tied to a string 15cm long. Initially the ball is held in position such that the string is horizontal. The ball is now released .A nail N is situated vertically below the support at a distance L. The minimum value of L such that the string will be wound round the nail is
Velocity of bob at C should be
here length of string =R, distance of nail below support =L , required minimum velocity to have vertical circle =
velocity of ball at bottom most point of circle is
equating the above two equations
squaring on both sides
5(R-L) = 2R
3R = 5L
L= R
distance of nail below support is
L= 15 = 9cm