JEE Mains 2020 Model Paper 2 New Pattern

A particle is attached to one end of a horizontal string of length ‘l’ whose other end is fixed to a point ‘O’ in the vertical plane. A nail P is fixed at a distance ‘r’ from point ‘O’ in the same vertical plane as shown. When the particle is released from rest, it just completes the vertical circle around nail P. Then the tension in the string just after touching the nail P is