1. The problem statement, all variables and given/known data A bridge rises 321m above the Arkansas river. Suppose you kick a rock horizontally off the bridge. The magnitude of the rock's horizontal displacement is 45.0 m. Fine the speed at which the rock was kicked. 2. Relevant equations Vi=Vx. Dx=45m. Dy=-321m 3. The attempt at a solution I know how to find the speed, but my question is on my book, it says that there is no initial vertical velocity. WHy? i think when you kick a rock off the bridge, there is a initial vertical velocity?! so why the vertical initial velocity is 0? hope you can explain it to me. Thanks.