Turn off daytime running lights, or reduce speed? Which saves more?

Which wastes more fuel? (and thus produces more carbon dioxide). This is a difficult to question to answer for a variety of reasons. The main reason is that a speed change from 71 mph to 70 mph is different than a reduction from 56 to 55 mph. First, let me be clear that the question…

A few tips for new faculty

So, we have some new faculty. New to the university, and new to teaching. What advise can I offer? Here are few things to consider: Never show fear. Students can sense fear. They see it as a sign of weakness. They may attack. If you are afraid, act like you are not. When in doubt,…

Basics: Free Body Diagrams

**Pre Reqs:** [Intro to Forces](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php), [Vectors](http://scienceblogs.com/dotphysics/2008/09/basics-vectors-and-vector-addition.php) Hopefully now you have an idea of what a force is and what it isn’t. What do you do with them? The useful thing to do with forces is to determine the total force acting on an object. At the beginning of the introductory physics course, you will likely…

Can you make an infinite number of playlists?

When mowing the lawn, I like to listen to podcasts. One of my favorites is [Buzz Out Loud](http://bol.cnet.com). This weekend, I was listening to episode 817 and one of the topics of discussion was MySpace and their DRM free music stuff. [Wired](http://blog.wired.com/music/2008/09/myspace-launche.html) had a description of what they were going to do. That is not…

MythBusters: How small could a lead balloon be?

On a previous episode of The MythBusters, Adam and Jamie made a lead balloon float. I was impressed. Anyway, I decided to give a more detailed explanation on how this happens. Using the thickness of foil they had, what is the smallest balloon that would float? If the one they created were filled all the…

Basics: What is a Force?

**Pre-reqs:** None. I intend to talk about forces and force diagrams, but there is a more fundamental question to address first. What is a force? Most texts define it as a push or a pull. That really isn’t a bad definition. Maybe a better (or maybe worse) definition would be “forces are things that change…

In a [previous post](/dotphysics/2008/09/basics-making-graphs-with-kinematics-stuff-part-ii/), I talked about how to plot kinematics data with a spread sheet and how to fit a quadratic function to the data. In the back of my head I remember “Don’t trust Excel”. I seem to recall someone claiming that Excel did not do a proper fit. To test this, I…

Basics: Relative Velocity

**pre reqs:** [Vectors and Vector Addition](http://scienceblogs.com/dotphysics/2008/09/basics-vectors-and-vector-addition.php) This was sent in as a request. I try to please, so here it is. The topic is something that comes up in introductory physics – although I am not sure why. There are many more important things to worry about. Let me start with an example. Suppose you…

Gravity, Weightlessness, and Apparent Weight

In my classes, I like to bring up the question: *Why do astronauts float around in space?* The most common response to this question is that they float around because there is no gravity in space. Some people take this a small step further and say that there is no gravity in space because there…

Basics: Making graphs with kinematics stuff part II

**pre-reqs**: [kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php) *I don’t think you need [part I of this](http://scienceblogs.com/dotphysics/2008/09/basics-making-graphs-with-kinematics-stuff.php) if you don’t want* So, you still want to make a graph with that kinematics data? You think that graphs on paper are too barbaric? Well, if you are ready, you can use a spreadsheet. But be careful. If you don’t know what you…