1. The problem statement, all variables and given/known data A soccer player kicks a rock horizontally off a 40m high cliff. If the player hears the sound of the crash 3.00s later, what was the initial speed given to the rock? assume the speed of sound in air is 343m/s. 2. Relevant equations Position of Y = -40m Time = 3s Position = Ut+.5at^2 3. The attempt at a solution To find the initial velocity of the rock, I know I must first find the displacement it covered in the x axis. However, I am not sure how to continue. I can use the equation Sx = U*t, but I do not know Sx or U(initial velocity). How can I derive initial velocity?