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On his journey home from a bombing raid in Germany during the second world war, flight sergeant Nicholas jumped without a parachute from his burning plane at a height of 18000 metres.

it took him 5.5 minutes to fall the first 17970 metres, most of it at about 55.6 m/s (terminal velocity)

From 30m from ground level, he travelled through dense pine trees and deep fresh snow before coming to a halt, taking approx 1.8seconds.

1. state the airman's acceleration before encountering the trees. then calculate his acceleration (deceleration) for the last 30 metres.

2. calculate what his acceleration (deceleration) would have been when he hit the ground if he had not been slowed down by pine trees and deep snow. assume that the time taken to come to a stop after hitting the ground would have been almost immediate. use a value of 0.1s for your calculations.

3. comment on the difference between your answer to 1 and 2

Feb 27, 2018

#1
+18080
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His acceleration (up to reaching terminal velocity) is just the acceleration of gravity=

9.8 m/s^2

2. Terminal velocity =   55.6 m/s     then he goes to ZERO m/s in 0.1 sec  (ouch!)

vf = vo + at       vf = vfinal = 0 (he stopped)    vo = original velocity of 55.6 m/s

0 = 55.6 + a(0.1)

a = - 556 m/s^2     (this will crush you like a bug under a steamroller)

Feb 27, 2018
edited by ElectricPavlov  Feb 27, 2018
#2
+18080
+1

vf = vo + at

0 = 55.6 m/s + a(1.8)

a = - 30.9 m/s^2

He had much more time to deccelerate through the trees (18 times more) so the DEcceleration is 1/18 of the decceleration of just hitting the ground and stopping in 0.1 s

Feb 27, 2018