I've got to admit, I'm very puzzled by this. It's not really a matter of choosing between the complex equation or the simple one, is it? If the single, somewhat complex equation p = m*a/(pi*r^2) is too difficult for you, don't you have to do not one, but three simple equations? F=m*a A=pi*r^2 p = F/A Either that, or you depend on someone else to do the preliminary calculations for you. And that means you have to take the accuracy of those preliminary calculations on faith. The complexity is still there, just not on display. Still, that's certainly a valid choice, and if your killer apps are the ones that hide as much of their complexity from you, there's no arguing with that.
For myself, there are many occasions when I can do what I need to do more readily with mc than with a graphical file manager that prettifies the interface, and in doing so hides elements that I need. That's what makes it a killer app for me.