Answer:
I can move even when you are still. I can be one or many.
They belong to me; they belong to you; They can make you feel happy or make you feel blue; They never end until the day you do.
If you drop me I'm sure to crack. But give me a smile and I'll always smile back.
If eleven plus two equals one, what is nine plus five equal to?
In we go, out we go. All around and in a row. Always, always steady flow. When we'll stop, you'll never known. In we go, out we go.
What covers its face with its hands, speaks no language, yet most known what it's saying?