Well, it takes one second to get every 10 meters (if g = 10 m / s 2 ), so one needs just 5.5 seconds. He would fall 137.5 meters (if my calculations are right) during that time.
5.6 seconds ;
It takes approximately 5.6 seconds for a parachuter to reach terminal velocity of 55 meters/second under the influence of gravity. This calculation assumes constant acceleration due to gravity until air resistance balances that force. The equations used to derive this include the force of gravity and the effects of air resistance on the parachuter.
;