A parachutist jumps from a height of 3.1 × 103m and falls freely for 10 s. She then opens her parachute, and for the next 20 s slows down with an acceleration of -4.5 m/s2. After that, she falls the rest of the distance to the ground at a uniform velocity.
(a) What is her velocity just before the parachute opens?
(b) At what altitude does the parachute open?
(c) What is the velocity of the parachutist, just before she strikes the ground?
(d) Calculate the time required for the whole descent.
(e) From what height would she have to fall freely in order to strike the ground with the same velocity as she does when wearing a parachute? (This is how parachutists are trained.)