how far will a rock fall in 15 sec if it is dropped 150 feet above the river at an initial speed of 24 ft per sec

Answer 1

s(t) = 24t + 16t^2
s(15) = 24*15 + 16*225 = 3960 ft

So, since it fell from only 150 ft, it will fall 150 ft. And, it won't take no steenking 15 seconds to hit the water.

Even if it is thrown upward, and the rock's height is

h(t) = 150+24t-16t^2

it will hit the water in about 4 seconds.