When a pencil is dropped it emits a range of natural frequencies i.e 200Hz 180Hz 150Hz 160Hz
1. Released from the pencil at the same time or at time intervals
2. Is there a pattern between the frequencies emitted ie is the 200 then 180 then 160Hz in decreasing value or are they random
3. What causes these different frequencies is it reflection of sound from the floor or is it more complicated than that .
The important principle this question is getting at is the Doppler effect (in this case for sound).
Have you ever stood on a street corner and listened to an ambulance pass by? As the ambulance gets closer to you, the 'pitch' of the sound gets higher. As soon as it passes you, the pitch immediately drops and goes lower. Same effect for race cars in NASCAR, etc... The frequency ...
The solution provides a good narrative explanation with examples.