1. A spelunker (cave explorer) drops a stone from rest into a hole. The speed of sound is 343 m/s in air, and the sound of the stone striking the bottom is heard 1.64 s after the stone is dropped. How deep is the hole? 2. A ball is thrown upward from the top of a 25.0-m-tall building. The ball's initial speed is 12 m/s. At the same instant, a person is running on the ground at a distance of 32.6 m from the building. What must be the average speed of the person if he is to catch the ball at the bottom of the building? 3. A roof tile falls from rest from the top of a building. An observer inside the building notices that it takes 0.18 s for the tile to pass her window, whose height is 1.8 m. How far above the top of this window is the roof? 2. Relevant equations Acceleratior = (Vf + Vi) / time displacement Vector average = (Vf + Vi) / 2 Vector Average = distance displacement / time displacement 3. The attempt at a solution No clue, if someone could help me that would be great. I can't do either of those 3 for some reason.