The acceleration of gravity on Earth is about 9.8 m/s².
That means that if air resistance is neglected, a falling body
smoothly gains 9.8 m/s of downward speed each second.
If our intrepid chutist lightly stepped out of the plane or was
gently pushed, so that his initial downward speed was zero
and grew by 9.8 m/s every second, then it took him ...
(55) / (9.8) = 5.6 seconds
to reach that particular downward speed.
