Re: [Phys-L] Definition of Mass

["John Clement" <clement@hal-pc.org>]

I think the question wanted a simple definition, and this is probably the
simplest, but it is gobbledy-goop to students who are not at the formal
operational level because they don't understand proportionality.  For the
intro class, multiple definitions may be very confusing.  Advanced students
can benefit from other ways of thinking.

Often students take equations like F_g=m g and think of g as just a
conversion factor, just like 2.54cm/inch.

As to wave particle duality, and the role of fields in modern physics,
students have to take existing ideas and use them to make new concepts.  It
can be complete disaster to just spring an alien idea on them.  So textbooks
are written to try to help students transition to new ideas, and it can be
helpful to use older concepts along the way.  99% of students will never
need to understand the role of fields, and a lot of practical science and
engineering works quite well with classical models.  Indeed even advanced
scientists use antique models in certain situations.  The model you use
should be appropriate to the situation and what you are trying to figure.

John M. Clement
Houston, TX


> From there it is easy to convince yourself that mass is the 
> constant of proportionality that connects momentum to velocity.
>
> Mass is also the constant of proportionality that connects 
> energy to the square of velocity, correct to second order.
>
> Mass is also the constant of proportionality in the famous 
> expression E = m c^2 ... which is a zeroth-order 
> approximation to equation [1].