What is the name of that "Perpetuum Mobile" which can be found in lots of offices as decoration...?

Question

... It is made of steel construction on which are 5 metal balls hanging down on wires. When you pull and release the last one, the last one on the other side repeat the action and it can go on forever.
You know what I mean?
How do you officialy call it?

Answer 1

It's called Newtons Cradle