The velocity of a body revolving in a vertical circle of radius ‘r’ at the lowest point is √(7gr) . The ratio of maximum to minimum tensions in the string is

Conserving energy - 1/2 mu2 +mg .2r = 1/2 mV2⇒ mu2 / r = m(√(7gr))2 / r - 4 mg = 3 mg.: Tmin + mg = mu2/r ⇒ Tmin = 3 mg - mg = 2 mg.: Tmax / Tmin = 8 mg / 2mg = 4 / 1