This is the correct equation for centripetal acceleration—acceleration towards the center of motion. in this case it isn't necessary to introduce a numerical factor. such a factor is often displayed explicitly as a constant k in front of the right-hand side; for example, a = kv2/r. as it turns out, k = 1 gives the correct expression. a good technique sometimes introduced in calculus-based textbooks involves using unknown powers of the dimensions. this problem would then be set up as [a] = [v]b[r]c. writing out the dimensions and equating powers of each dimension on both sides of the equation would result in b = 2 and c = −1.