Editing Rotational frequency (section)

==Related quantities==
[[Tangential speed]] <math>v</math> (Latin letter [[v]]), rotational frequency <math>\nu</math>, and [[Polar coordinate system|radial distance]] <math>r</math>, are related by the following equation:<ref>{{Cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/rotq.html|title = Rotational Quantities}}</ref>
<math display=block>\begin{align}
v &= 2\pi r\nu \\
v &= r\omega.
\end{align}</math>

An algebraic rearrangement of this equation allows us to solve for rotational frequency:
<math display=block>\begin{align}
\nu &= v/2\pi r \\
\omega &= v/r.
\end{align}</math>

Thus, the tangential speed will be directly proportional to <math>r</math> when all parts of a system simultaneously have the same <math>\omega</math>, as for a wheel, disk, or rigid wand. The direct proportionality of <math>v</math> to <math>r</math> is not valid for the [[planet]]s, because the planets have different rotational frequencies.