Question

A stone of mass m is tied to a string and is moved in a vertical circle of radius r having speed v at the lowest point. The tension in the string when the stone is at the lowest point is

Answer 1

Answer: T = 6mg

V at the lowest point is (5gr)*1/2....(1)

By using

T - mgcostheta = mv*2/r...... (2)

At lowest point angle is 0°

Put (1) in (2)

After solving you will get 6mg

Answer 2

so according to diagram

T=mg+mv2/r (mv2/r=centrifugal acceleration)

so T=m(g+v2/r)

hope it helps