Question

You’re at the park watching a child on a swing (you’re standing directly in front of the child). The kid has an annoying whistle that he’s blowing. Where, in his motion, do you perceive the lowest frequency? Where, in his motion, does he perceive the lowest frequency? Explain your answers.

thanks!

Answer 1

The frequency is increasing  when the child on the swing is coming towards you and is highest when he has reached the apex in the front. Similarly, when he is going back the frequency is decreasing and is lowest when he has reached apex at the back.

It is according to the Doppler shift. According to Doppler effect, the perceived frequency when the source is moving with speed v is given by:

f’ = f* c/(c -+ v)

where c is the speed of sound.

the denominator is - when he is moving towards you and + when he is moving away from you.

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