Sound

When me are riding my bicycle, and someone gets in my way, I ring my bell. The other person hears my bell, and jumps out of the way. The bell has made sounds that have travelled through the air into that person ears.

What is sound? I can find out if i touch my bicycle bell white it is ringing. I can find that the outside of the is moving quickly, or vibrating. The bell passes on these vibrations to the air as waves of the sound. In the air, the sound waves move out in all directions, rather like the ripples in a pond moving out after you have thrown in a stone.
The picture shows what the bell looks like inside. When you press the lever to ring the bell, the toothed gears make the middle part spin round. The little loose weights at the ends fly out and hit the bell, making it ring.