A sounding body emitting a frequency of $$150$$ Hz is dropped from a height. During its fall under gravity it crosses a balloon moving upwards with a constant velocity of $$2$$ $$m/s$$ one second after it started to fall. The difference in the frequency observed by the man in balloon just before and just after crossing the body will be: (given$$ that velocity of sound $$=$$ $$300$$ $$m/s$$; g $$=$$ $$l0$$ $$m/s2)

Question

A sounding body emitting a frequency of $$150$$ Hz is dropped from a height. During its fall under gravity it crosses a balloon moving upwards with a constant velocity of $$2$$ $$m/s$$ one second after it started to fall. The difference in the frequency observed by the man in balloon just before and just after crossing the body will be: (given$$ that velocity of sound $$=$$ $$300$$ $$m/s$$; g $$=$$ $$l0$$ $$m/s2)

Infinity Learn · Accepted Answer

f $$=$$ $$f0(v$$±$$v0v$$±$$vs)When$$ approaching: fa $$=$$ $$150$$[$$300+2300-10$$]When receding: fr $$=$$ $$150$$[$$300-2300+10$$]⇒ fa $$=$$ fr $$=$$ $$12$$

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