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A train moves towards a stationary observer with speed 34 m / s . The train sound a whistle and its frequency registered by the observer is f 1 . If the train' s speed is reduced to 17 m / s , the frequency registered is f 2 . If the speed of sound is 340 m / s , then the ratio of f 1 f 2 is

Options

  1. A18 / 19
  2. B1 / 2
  3. C2
  4. D19 / 18

Correct answer

D. 19 / 18

Step-by-step solution

f 1 = v v - v s f ⁡ = 340 340 - 34 f ⁡ = 340 306 f & f 2 = 340 340 - 17 f ⁡ = 340 323 f f 1 f 2 = 19 18

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