1. The problem statement, all variables and given/known data A ball is tied to a cord and set in rotation in a vertical circle. Prove that the tension in the cord at the lowest point exceeds the tension in the cord at the highest point by six times the weight of the ball. 2. Relevant equations U1+K1=U2+K2 F=mv^2/r a=-V^2/r 3. The attempt at a solution From U1+K1=U2+K2 I get: (1/2)mv^2=2mgr+(1/2)mv2^2 I also took a look at the forces to get: T1=mg-mv^2/r and T2=-mv^2/r-mg I have tried substituting all sorts of ways, but have been unable to prove what is asked for. I asked my teacher for help, but he said that I was on the right track and I just had to keep plugging stuff in.