Wave Motion 4 Question 11

11. A police car moving at 22m/s chases a motorcyclist. The police man sounds his horn at 176Hz, while both of them move towards a stationary siren of frequency 165Hz. Calculate the speed of the motorcycle, if it is given that the motorcyclist does not observe any beats (speed of sound =330m/s ).

(2003, 2M)

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(a) 33m/s

(b) 22m/s

(c) Zero

(d) 11m/s

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Answer:

Correct Answer: 11. (b)

Solution:

  1. The motorcyclist observes no beats. So, the apparent frequency observed by him from the two sources must be equal.

f1=f2176(330v33022)=165(330+v330)

Solving this equation, we get v=22m/s



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