This applet simulates Newtonian mechanics with gravity.
The objects are massive pieces of text (with their center of mass located at the lower left corner of the word) that feel gravitational forces. The "SU" and "Physics" have significant mass, while the dots (periods) have negligible mass -- they are so-called 'test particles'.
Try clicking the mouse in the applet.
Try clicking the mouse several times in one place. [The divergence of paths can be used to demonstrate "chaos" (sensitivity to initial boundary conditions) and tidal forces (note the spreading of a mass of particles).]
Try clicking in the upper left and upper right corners.
Go HERE for different initial test particles.