What use is made of this fact?
The tramping of horses or the rumbling of cars and wagons, when at a distance, may be heard by placing the ear near the ground.
Do all solid substances produce the same amount of sound when struck?
No; soft substances, such as lead and wood, produce but little sound; while hard substances, such as copper, bell-metal, and glass, produce much more sound.
What are hard bodies, producing much sound, called?
They are called sonorous bodies.
Is a bell a very sonorous body?
Yes; a bell is one of the most sonorous bodies that we have.
Why does a bell ring when struck?
Because the stroke causes the particles of the bell to vibrate.