In physics, differentiation is used to figure out the rate of something. To put it simply, it is used to figure out the rate and slope of the tangent at a certain point on a curve, among other things. Because of this, you should use differentiation whenever you need to figure out how fast something is changing. Differentiation includes things like speeds and accelerations, slopes and curves, and so on. These are Rates of Change, which are set on a local level.