Dimensions

Dimensions and Units

Every expression you write down that tries to describe something about the real world has to be dimensionally consistent. After all, what does the expression 5mi hr +3ft mean? Or an equation such as 6sec−2km = 4kg? Or the statement that the distance from here to downtown Miami is 8? Answer: Nothing! (Well, maybe in the last case there is a context, and you know that the speaker meant eight miles, but often you don't know this, and it means there's a mistake.)

You can figure out correct units for something just by solving a little algebra.