Which of the following best states
what a physical quantity is? (A) A physical quantity is a
measurement of something. (B) A physical quantity is
something that can be measured.
These two answer options may seem
to be saying the same thing. They are different, though. Say that we have some physical
object like this. This object has various properties
like mass or speed or height. And say that we were to measure
these particular quantities. Our results might be as
follows. And now notice that we have two
columns. The first column shows the thing
that is being measured, and the second column shows the measurement of that
thing. Answer option (A) is talking about
the measurement itself. That would be our second
column. Answer choice (A) is saying, for
example, that 8.1 kilograms is itself a physical quantity, so as zero meters per
second, and so on.
Option (B), on the other hand, is
talking about the other column, mass and speed and height in general. This is the best definition of a
physical quantity. Rather than being the measurement
of something itself, a physical quantity is something that can be measured.