Definition of momentum\\

It is convenient to define a physical quantity called momentum, usually indicated by the symbol $p$, as the product of its mass $m$ by its velocity $\vec{v}$

\begin{equation}

\vec{p} = m \vec{v}

\end{equation}

The momentum is a vector quantity which has the same direction as the velocity of a body.

The unit of measurement of momentum in the SI system is the product of the units of mass and velocity and thus is the kg m/s.

A new form of the Second Newton’s Law\\

Newton’s Second Law can be expressed in terms of change in momentum:

\begin{equation}

\vec{F}_{net} = m \vec{a} = m \frac{(\vec{v}_{final} -\vec{v}_{initial} )}{\Delta t} = \frac{m \vec{v}_{final} – m \vec{v}_{initial} }{\Delta t} = \frac{\vec{p}_{final} -\vec{p}_{initial} )}{\Delta t}

\end{equation}

which can be written in the more compact form

\begin{equation}

\vec{F}_{net} = \frac{\Delta \vec{p}}{\Delta t}

\end{equation}