Question

A key of a mechanical piano is struck gently and then struck again but much harder this time. In the second case

• A. both loudness and pitch will remain unaffected
• B. sound will be louder and pitch will also be higher
• C. sound will be louder but pitch will be lower
• D. sound will be louder but pitch will not be different

Answer 1

Answer: (D)

sound will be louder but pitch will not be different

When the key of a mechanical piano struck harder, the vibrations caused are more resulting in larger amplitude of the wave that propagates from the key.
Loudness depends on the square of the amplitude of the wave.
That is, $loudness\propto {\left(amplitude\right)}^2$
Amplitude is the size of the vibration, and this determines how loud the sound is. Larger vibrations make a louder sound.
Pitch of the sound depends on the frequency of the wave which is not change when the key is struck harder.