1. The problem statement, all variables and given/known data Hello, I am a bit confused on when rotational kinetic energy exists and when linear kinetic energy exists. For example when we spin a string with a ball attached to the end it has kinetic energy of 0.5mv^2 of the ball when we were solving for velocity of the ball at certain points in the vertical circle of the ball. But know that i learned rotational motion, why don't we consider rotational energy in that example instead of just mgh and 0.5mv^2? There was a question where there was a ball attached to a bar and the system of bar and ball attached to the bar are moving and we used just rotational kinetic energy to solve the question and didn't account for 0.5mv^2. 2. Relevant equations 3. The attempt at a solution I was thinking maybe it has to do with something about the string maybe being negligible or something but still not sure. I would like some clarification on this matter please.