Review of Calculus Principles

 

In order to understand dynamics, you are going to have to understand basic principles of integral and derivative calculus. For this reason, I have posted some notes on derivatives and integrals. When you understand the principles, you should be able to complete the practice problems I have included.

Reference Material

I’m going to offer you two different ways to review concepts of differentiation and integration. The first is a document that I wrote a few years ago. The second is a series of beautiful videos created by Grant Sanderson (3 Blue 1 Brown). You may choose either of these approaches, or both.

The Document

PDF logo. Links to calculus review notes.

This document discusses how to think about the derivative and integral, based on the definitions of the operations. I have created video versions of parts of the calculus review in case you prefer to listen/watch the material, rather than read: Definition of Derivative; Check Your Understanding of Derivative; Check Your Understanding of Integral.

The Videos

Here are those gorgeous videos I mentioned. By illustrating how one would calculate the area of a circle using calculus-like thinking, Sanderson elegantly illustrates the Fundamental theorem of calculus.

In this second video, he illustrates the derivative by thinking about the “velocity” of a car. I do the same in my notes, but Sanderson’s is so much more beautiful. I just have two small beefs with the video.  First, he uses the word “velocity” when he should say “speed.” Secondly, I disagree with the paradox he talks about. There’s nothing inconsistent about a moving object having zero velocity (motionless) for just an instant. If you want, you can stop watching after time 10:25.

And finally, a video on integration and its relationship with the derivative (i.e. the Fundamental theorem of calculus).

Take-Aways, Derivative

  • A time derivative is a measure of how fast something is changing at some instant.
  • If we have a plot of some function with respect to the dependent variable t, then the derivative of the function with respect to t, evaluated at t=t0, is the slope of the tangent line at t=t0.
  • If something is increasing with respect to time, then its time derivative is positive.
  • If something is decreasing with respect to time, then its time derivative is negative.
  • When something is NOT changing, its time derivative must be zero.

Take-Aways, Integral

  • One can think of an integral as the opposite of derivative, an “anti-derivative.”
  • One can think of an integral as a signed area under the curve.
  • When the integrand (function you’re integrating) is positive, the integral of that function should be increasing.
  • When the integrand is negative, the integral of that function should be decreasing.
  • When the integrand is zero, the integral should not change, at least for a brief moment.
  • For indefinite integrals, there is an arbitrary constant of integration.

Practice Problems

To help you understand differentiation and integration at a level that will help you understand dynamics, you should try answering these four practice problems.

Answers to Practice Problems

After you work out the practice problems you should check your answers. I have answers posted in two formats below. The PDFs are there if you want a quick look at the answers. I have also posted videos in case you want to hear my explanation.

Video for Problem A:

Video for Problem B:

Video for Problem C:

Video for Problem D: