20 Greatest Equations

This should actually be the 20 Greatest Physics Equations.

I'm posting this to my personal log just to get people who would normally avoid physics, math or science to take a look.

Don't worry, the only ones I think are 'generally useful' and that people should know are:

Newton's second law (force = mass x acceleration). if more people understood this, they would take more effort to not crash automobiles into each other or stationary objects.

Pythagora's theorem. You want to know this if your cutting down trees so they don't hit your house. I would add all the trig functions (sine, cosine, tangent). No one seems to know how to use trig after high schoool, but then they do stupid things like crush their house/car when they chop down trees.

Circumference of a circle. everyone should know this. I refuse to tell people when they ask, but I will go find it in a dictionary with them. Sort of like teaching someone how to fish.

Ideal gas law - PV=nRT. OK, not generally useful, but its why aerosol cans explode in fires and a can will be crushed if you take it 14-28 feet below the surface of the water. You need to know this if you SCUBA dive.