It is given that when the ball moves with speed \(6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) the tension in the string \(Q B\) is three times the tension in the string \(P B\). Calculate the radius of the circle.
The ball now moves along this circular path with the minimum possible speed.
State the tension in the string \(P B\) in this case, and find the speed of the ball.