Answer:
1. When the Ruler is bent the energy stored in it will be potential energy, When the ruler will be released this potential energy will be then converted into the Kinetic energy as a result the ruler will move Vibrations.
2. Hard or wiggly. Some of the ruler is wiggly or plain.
3. Yes, you will hear and feel the vibration of the ruler.
4. Yes, it will stop.
5. When you held the ruler, you stopped the air around it from vibrating, thus diminishing the sound.
Hope it helps!
