Physics/Newton/Second Law  From Wikibooks Jump to: navigation,
search  In the First Law of Motion, we have worked with the case
where no forces are acting on a mass. However, that is normally
useless because we do not normally work with such cases, since
such cases are so simple.  When we need to work with forces that
can change how a mass moves, we will need to use the Second Law
of Motion. However, before we can understand the Second Law, we
have to define some terms used. The first of these is the word
magnitude. Basically, magnitude refers to the size of something.
Magnitude is usually given as a number, since most of the time
magnitudes are defined by comparing the thing measured to a
widely recognised standard. For example, the mass of something
is usually given as how many times heavier it is compared to a
certain lump of metal kept in France. (This is the original
definition of the kilogram)  Next in the list of terms to define
are scalar and vector. Simply, the difference between them is
that vectors