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NTA Abhyas JEE Main2020PhysicsMotion in One DimensionPractice

A helicopter takes off along the vertical with an acceleration a = 3 m s - 2 and zero initial velocity. In a certain time t 1 , the pilot switches off the engine. At the point of take-off, the sound dies away in time t 2 = 30 s . Determine the velocity v of the helicopter (in m s - 1 ) at the moment when its engine is switched off, assuming that the velocity c of sound is 320 m s - 1 .

Correct answer

80

Step-by-step solution

t 2 = t 1 + a t 1 2 2 c t 1 = c a 2 + 2 c a t 2 - c a v = a t 1 = a c a 2 + 2 c t 2 a - c a = c 2 + 2 a c t 2 - c = 80 m s - 1

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