Here are some physics demos written in GlowScript. These happen to be
essentially 2D, so presumably they could be implemented with a 2D canvas,
without having to use WebGL.
Pull two pucks across a low-friction surface; an illustration of the fact
that the net force governs the motion of the center of mass no matter where
the force is applied, and that the extra (rotational) kinetic energy of the
rotating puck is due to the force acting through a larger distance: http://www.glowscript.org/#/user/Bruce_Sherwood/folder/MI/program/09%5fTwoPucks