1. The problem statement, all variables and given/known data A rock falls of the cliff, 3.4 seconds later, you can hear the rock hitting the ground. Assuming the speed of sound is 340 m/s, how high is the cliff? 2. Relevant equations Delta X = Vot + 0.5at^2 2a Delta X = V^2 - Vo^2 3. The attempt at a solution I don't know how to start. The height of the cliff is unknown and the time it took the rock to hit the ground is unknown. Initial velocity is zero and that's all I can say. I don't know where to start. Perhaps I am missing something.