A helicopter is hovering at rest above horizontal ground at the point H. A
Parachutist steps out of the helicopter and immediately falls vertically and freely
under gravity from rest for 2.5 s. His parachute then opens and causes him to
immediately decelerate at a constant rate of 3,9 m/s^2 for T seconds (T < 6), until
his speed is reduced to V m/s, He then moves with this constant speed V m/s
until he hits the ground. While he is decelerating, he falls a distance of 73.75 m.
The total time between the instant when he leaves H and the instant
when he hits the ground is 20 seconds.
The parachutist is modelled as a particle.
Find the Speed of the parachutist at the instant when his parachute opens
Find the value of T
I can't seem to figure it out, any ideas?