Normal component
= Normal component
{title2=$w_N=(w\cdot n)n$}
The normal component is the <orthogonal projection> of a <vector> onto the local normal space. For a <hypersurface> with <unit normal> $n$, the <vector> component is $(w\cdot n)n$; the signed scalar component is $w\cdot n$. These two meanings must be distinguished. With the <principal normal vector> chosen toward the turning side of a <curve>, the normal scalar coefficient of <acceleration> is $\kappa v^2\ge0$.