Question

Why does the pitch of sound increases when a nail is hammered into a wall ?

Answer 1

Because a part of hammer's kinetic energy is turned into heat. 
This causes molecules in both the hammer and the nail to oscillate, and since temperature is proportional to the kinetic energy of object's particles, its temperature increases.

Answer 2

The pitch of the sound increases because:

• Pitch depends upon frequency.
• When nail is hammered it produces an increasing frequency which is equal to the vibrations per second
• This increasing frequency results in increasing pitch is directly proportional to frequency.
• Hence the pitch increases.

Hope it helps you

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