You drop a rock off the top of a building. it takes 3.4 s to hit the ground. what is the velocity at impact (final velocity)? i need !

-- The acceleration of gravity (on Earth) is 9.8 m/s².

-- That means that during every second an object falls,
    it adds 9.8 m/s of speed.

Now !    If it adds 9.8 m/s of speed every second, then
              how fast is it falling at the end of  3.4 seconds ?

This is as close as I can bring you to the answer
without dropping it at your feet, or handing it to you
on a golden tray.