How does the relative motion of a motorcycle affect the frequency of the sound heard by an observer on the sidewalk?

As per Doppler's effect of sound we know that when source and observer moves with some relative velocity with respect to each other then the frequency of sound that observer will hear is different from the actual frequency of sound and it is known as Doppler's effect.

So here when relative motion of bike is towards the observer the frequency is given by

so the frequency heard by the observer will be more than actual frequency in this case

So now when relative motion of bike is away from the observer the frequency is given by

from above equation we can say that in this case frequency heard by observer will be less than actual frequency

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explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

no

sodium is solid at rt