# Definition of Mass

Q:
How can we define mass in a concrete and much more conceptual way than the commonly use definition of the amount of matter contained in a body /system?
- Yash More (age 17)
Kolkata, West Bengal, India
A:

That's a great question, but not easy. Here's a try.

Say that you're trying to fit phenomena into a framework like Newton's laws, including a=F/m. You can try to make some calibrated F's, e.g. the push from a spring compressed a specific amount. Then you assign m's to objects based on how much they accelerate under that F. You check whether this is self-consistent by then taking the same objects and applying different F's to them. Do you get the same m's for each of the different F's? if so, then the framework works and you've defined your m's.

Actually, I left out one step. This procedure really gives a bunch of ratios of m's, and you have to pick one to represent your unit mass.

What about the usual fuzzy definition? That can be converted to a testable proposition, that when you put together objects the combined mass is the sum of the separate masses. That proposition works very well in classical physics.

Mike W.

(published on 10/16/2017)

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