I think rubbing two pieces of woods together will have more friction than wood rubbing against a smooth metal.
<u>Explanation:</u>
The friction offered by surfaces has a great role in deciding the ease of movement of objects along the surface.
The friction of the surface depends upon its roughness. Rough surfaces offer greater friction than smooth surfaces.
In this question wooden pieces have greater friction than that of smooth metal. So rubbing two wooden pieces together will have greater friction than rubbing a wooden piece against a smooth metal.
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Answer:
The wavelength of frequency of the sound are closer to each other
Or
The frequency of the sound increases as it moves towards you
