1. The problem statement, all variables and given/known data A boy ties a rock to a 0.95 m string and swings it in a horizontal circle directly over his head so that it completes one revolution every 0.75 s. What is the tension in the string? So we know r and we can calculate V, but that's all I can deduce 2. Relevant equations Fc=(mv^2)/r V=(2*pi*r)/t 3. The attempt at a solution 2*pi*.95/.75= 7.9587 m/s That's how far I got. I know the masses cancel with ma=mv^2/r but then I end up finding the acceleration. Help?