Atrain starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of 24 m/s.

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.