When the ball is first thrown, its kinetic energy is highest and its potential energy is lowest. As the ball rises, its kinetic energy decreases and its potential energy increases because it's slowing down as it goes higher. As the ball goes as high as it can, it stops momentarily; that is when the ball's potential energy is full, and it's kinetic energy is low. Then when the ball begins to fall back down, its potential energy is getting lower, and its kinetic energy is growing. Right before the ball hit the ground, the kinetic energy was at its highest, and its potential was lowest. Then when it hit the ground, there was no kinetic or potential energy.
