
Patrick D. answered 04/25/17
Tutor
5
(10)
Patrick the Math Doctor
We need to know how fast he was falling at the instant he pulled the cord.
That is initial velocity.
acceleration = final velocity - initial velocity
-------------------------------------
time
10 = ( final velocity - initial velocity)/4
40 = final velocity - initial velocity
40 + initial velocity = final velocity
When you find that number add it to 40 to get your answer.
We can also get the answer if we know how far he fell during the 4 seconds
between the time he pulled the cord to when the parachute opens.