Momentum

Momentum is the modern English word used for translating the phrase "quantity of motion" that Sir Isaac Newton uses on the very first page of his great book, the Principia.

^{1}So to understand motion WikiMechanics starts by using sensation to define the momentum as follows. Consider some particle P characterized by its wavevector $\overline{ \kappa }$ and the total number of quarks it contains $N$. Report on any changes relative to a frame of reference F which is characterized using $\tilde{ \kappa }$ the average wavevector of the quarks in F. Definition: the**momentum**of particle P in reference frame F is the ordered set of three numbers$\begin{align} \overline{p} \equiv \frac{h}{2\pi} \left( \overline{ \kappa }^{ \sf{P}} \! - N^{ \sf{P}} \, \tilde{ \kappa }^{ \sf{F}} \right) \end{align}$

where $h$ is a constant. The norm of the momentum is marked without an overline

$p \equiv \left\| \, \overline{p} \, \right\|$

If $p=0$ we say that P is **stationary** or **at rest** in the F-frame. Alternatively, if $p \ne 0$ then we say that P is in **motion**.

*contrast*between a particle and its reference frame. A signal for attention!Related WikiMechanics articles.

Velocity | Momentum is traditionaly understood as a product of the mass and a velocity. You can jump ahead to a discussion about velocity to see how the customary approach works with the WikiMechanics definition of momentum given above. |