1. The problem statement, all variables and given/known data A 500g rock is thrown straight down from a bridge and hits the water 5.2 m below. If the rock strikes the water at a speed of 12.5 m/s, what was the initial speed of the rock? 2. Relevant equations I'm not totally sure... 3. The attempt at a solution I have no idea how to even start this. Could someone help me start to solve it, please?