There seems to be a misunderstanding. There is no standard physics apparatus known as a "Demonstration Balance." It's possible that you're thinking of a different term, or that it's a less common piece of equipment.

Could you clarify what you mean by "Demonstration Balance?" Maybe you're referring to:

* A balance scale: This is a common piece of equipment used to demonstrate the principles of mass, weight, and equilibrium.

* A beam balance: Similar to a balance scale, but uses a horizontal beam to demonstrate the same concepts.

* A specific piece of equipment with a unique name: If you can provide more details about the equipment, I might be able to assist you.

Please provide more context about the apparatus you're looking for, and I'll be happy to help.