1. The problem statement, all variables and given/known data Mass m ball hangs on the L length thread. This system is turned up by angle alfa from the vertical. What is the stretch force when the ball passes the state of balance (where ball's kinetic energy is the biggest)? 3. The attempt at a solution At the alpha position, potential energy = mgL(1 - cos(alpha)). This gets converted into KE at the bottom. So, m*v^2/2 = mgL(1 - cos alpha). This gives the velocity at the balance point. Now the stretch force will not only be balancing the weight but also the centrifugal force which is m*v*v/L. So T = mg + m*v*v/L = mg(3 - 2*cos alpha). Is anything Ok in my solution? Isn't here any mistakes? Thanks in advance.