Suppose you're driving along a straight, smooth, level stretch of highway with a constant velocity [itex]v[/itex]. There is a cup of some fluid in your cup holder. How would you go about finding the angle [itex]\theta[/itex] that the surface of the fluid makes with the bottom of the cup as a function of [itex]v[/itex]? And what if you started out with a velocity [itex]v_0[/itex] at time [itex]t=0[/itex] and then accelerated at a constant rate [itex]a[/itex]? Can we find [itex]\theta(t)[/itex] without much sweat?