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We use observed radial profiles of mass surface densities of total,$\Sigma_g$, & molecular, $\Sigma_{\rm H2}$, gas, rotation velocity & starformation rate (SFR) surface density, $\Sigma_{\rm sfr}$, of the molecular-rich($\Sigma_{\rm H2}\ge\Sigma_{\rm HI}/2$) regions of 16 nearby disk galaxies totest several star formation laws: a Kennicutt-Schmidt law, $\Sigma_{\rmsfr}=A_g\Sigma_{g,2}^{1.5}$; a Constant Molecular law, $\Sigma_{\rm sfr}=A_{\rmH2}\Sigma_{\rm H2,2}$; the turbulence-regulated laws of Krumholz & McKee (KM05)and Krumholz et al. (KMT09), a Gas-$\Omega$ law, $\Sigma_{\rmsfr}=B_\Omega\Sigma_g\Omega$; and a shear-driven GMC Collision law,$\Sigma_{\rm sfr}=B_{\rm CC}\Sigma_g\Omega(1-0.7\beta)$, where $\beta\equiv d{\rm ln} v_{\rm circ}/d {\rm ln} r$. If allowed one free normalizationparameter for each galaxy, these laws predict the SFR with rms errors offactors of 1.4 - 1.8. If a single normalization parameter is used by each lawfor the entire galaxy sample, then rms errors range from factors of 1.5 - 2.1.Although the Constant Molecular law gives the smallest errors, the improvementover KMT, Kennicutt-Schmidt & GMC Collision laws is not especially significant,particularly given the different observational inputs that the laws utilize andthe scope of included physics, which ranges from empirical relations todetailed treatment of interstellar medium processes. We next search forvariation of star formation law parameters with local & global galacticdynamical properties of disk shear rate (related to $\beta$), rotation speed &presence of a bar. We demonstrate with high significance that higher shearrates enhance star formation efficiency per local orbital time. Such a trend isexpected if GMC collisions play an important role in star formation, while anopposite trend would be expected if development of disk gravitationalinstabilities is the controlling physics.

A Test of Star Formation Laws in Disk Galaxies. II. Dependence on dynamical properties