"you and your physics major roomate become involved in a sinister plot to drop water balloons on students entering your dorm. Your room is 70 Feet above the sidewalk. You plan to place an X on the sidewalk to mark the spot a student must be when the balloon is dropped. The student will walk the distance from the X to the place the balloon hits in the time the balloon falls. After observing several students, you conclude most students walk at about 2.1 m/s when coming into the dorm."
How far from the impact point do you place the X?
How do I start this..