Conceptual Understanding in Introductory Phyiscs II

This post is the second in this series. You can read the background on this series in my previous post. I hope the questions in this series promote some discussion of what the goals of contemporary introductory physics should be these days.

Here is the next question. It has multiple parts.

In one sentence, explain what we mean when we say a physical quantity is constant. In one sentence, explain what we mean when we say a physical quantity is invariant. In one sentence, explain what we mean when we say a physical quantity is conserved. Give an example of a physical quantity that is constant, invariant, and conserved. Give an example of a physical quantity that is invariant, but not necessarily conserved. Finally, give an example of a physical quantity that is conserved, but not necessarily invariant.

It is important for students to understand the distinctions among these three terms (constant, invariant, and conserved). They are not interchangeable and using them correctly requires a rather deeper understanding than students usually get. As I said last time, I won’t disclose answers here but feel free to kick things around in the discussion area.

Go!


3 Comments on “Conceptual Understanding in Introductory Phyiscs II”

  1. […] same value before and after something happens, like an interaction.” I mentioned this in a previous post. There is still one piece missing, and that is the concept of “system.” I defined […]

  2. achmorrison says:

    I have to admit that I don’t think I ever even use the word invariant when I am teaching introductory physics. Am I doing it wrong?

    • heafnerj says:

      Wrong? That’s your call. I think invariance is an important concept to understand within the contexts of vector analysis and relativity, two frameworks that are important to contemporary physics. If your course doesn’t include these frameworks then there may indeed be no real need for the concept.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s