Question

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 29.0 m below the point where the rock left your hand? Ignore air resistance.

Answer 1

So the issue is what speed did you throw it with?

it takes 3.4 seconds to get to the apex...at the top it has zero speed.
vf=vi+gt
0=vi-9.8*3.5
solve for the vi initiual velocity.

then
final KE =initial KE +initial PE
1/2 m vf^2=1/2 m vi^2 + mg*28
solve for vf

Answer 2

7.4