A helicopter takes off vertically with acceleration 3 m / s 2 from rest. The pilot switches off the engine at time t 1 ; at the take-off point the sound dies away 22 s after take-off. Taking the vel

Question

A helicopter takes off vertically with acceleration 3 m / s 2 from rest. The pilot switches off the engine at time t 1 ​ ; at the take-off point the sound dies away 22 s after take-off. Taking the velocity of sound as 300 m / s , the velocity of the helicopter at switch-off is:

TestHub · Accepted Answer

t 1 ​ + 300 1.5 t 1 2 ​ ​ = 22 gives t 1 2 ​ + 200 t 1 ​ − 4400 = 0 , t 1 ​ = 2 − 200 + 40000 + 17600 ​ ​ = 2 − 200 + 240 ​ = 20 s , so v = 3 × 20 = 60 m / s .

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