When charge Q1 is placed at point P1, the resulting potential at point P is V1. When Q2 is placed at point P2 after Q1 is in position at P1, the resulting potential at P becomes V2. What is the potential at point P if charge Q1 is then removed

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.