Spring constant
= Spring constant
{title2=$k$}
The spring constant is the positive proportionality coefficient in the ideal <spring> <restoring force> $F=-kx$. Its SI unit is newtons per metre. With a constant attached <mass> $m$, it sets the <angular frequency> $\omega=\sqrt{k/m}$ of <simple harmonic motion>. Doubling $k$ doubles the restoring <force> at a fixed <displacement>, but increases that <angular frequency> only by a factor $\sqrt2$.