Question

Choose the correct answer.
A commando jumps from the helicopter, after about 500 m his parachute opens a
reduces to 1/4 of the previous velocity. He covers next 1000 m with this speed bef
ground. If the total time of flight is 30 sec, with what velocity had he started falling​

Answer 1

Given : A commando jumps from the helicopter, after about 500 m his parachute opens a  reduces to 1/4 of the previous velocity. He covers next 1000 m with this speed reach ground.  the total time of flight is 30 sec,

To Find : with what velocity had he started falling​

Solution:

Let say Commando started with Velocity V

after t secs  his Speed Become = V + gt

V² - U²  = 2aS

=( ( V + gt)² - V² )   = 2* g * 500

=> g²t²  + 2Vgt  = 1000g

=>  gt²  + 2Vt  = 1000

=> 10t² + 2Vt = 1000

=> 5t² + Vt = 500

=> V = (500 -  5t²)/t

Now Velocity =  ( V + gt)/4

Distance = 1000 m

Time =  1000/  (( V + gt)/4) = 4000/ ( V + gt)

total time =  30 sec

=> 30 - t  = 4000/ ( V + gt)

=> (30 - t)(V + gt) = 4000

=>  (30 - t)(V + 10t) = 4000

=>  (30 - t)((500 -  5t²)/t + 10t) = 4000

=> (30 - t)(500 - 5t²  + 10t²) = 4000t

=> (30 - t)(500 + 5t²) = 4000t

=> (30 - t)(100 +  t²) = 800t

=> t³  - 30t² +900t - 3000 = 0

=> t ≈ 3.7418

V = (500 -  5t²)/t  = 114.91 m/s

Initial Velocity = 114.91 m/s

velocity he started falling​  =  114.91 m/s

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Answer 2

Answer:

Step-by-step explanation: