1. The problem statement, all variables and given/known data I have 2 rocks. One is thrown straight up from a cliff's edge. A certain amount of time later another rock is dropped from the cliffs edge. I need to calculate the initial velocity of the rock 1 so that they hit the ground simultaneously. I have the cliff hight, the time after rock 1 when rock 2 was thrown, and acceleration of course. I just need some pointers as I can't seem to get my thinking behind it. Cheers!!!!