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What happens when you take some basic, introductory physics and apply them to cool things you see? Dot Physics happens. This blog looks at movies, experiments, demos and other topics typically aimed at the introductory physics level.
Rhett Allain is an Associate Professor of Physics at Southeastern Louisiana University. He
enjoys teaching and talking about physics. Sometimes he takes things apart and can't
put them back together.
September 30, 2008
Category: physics
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.
Posted by Rhett Allain at 10:43 PM • 2 Comments • 1 TrackBacks
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:
Posted by Rhett Allain at 9:44 PM • 0 Comments • 0 TrackBacks
Category: physics
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 look at cases where the total force is the zero vector. This is called equilibrium. Even if you are looking at cases where the forces don't add up to the zero vector (I say that instead of just "zero" to remind you that the total force is still a vector). Physicists like to represent forces on an object by drawing a Free Body Diagram. This is simply a representation of an object and a graphical representation of all the forces acting on that object.
Posted by Rhett Allain at 11:55 AM • 7 Comments • 0 TrackBacks
September 28, 2008
Category: science
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 my point. The point is the claim that you could make an infinite number of playlists. How about I calculate (or estimate) the number of different playlists one could make.
Posted by Rhett Allain at 10:34 PM • 1 Comments • 0 TrackBacks
September 26, 2008
Category: physics
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 way, how much could it lift?
Posted by Rhett Allain at 9:41 AM • 0 Comments • 0 TrackBacks
Category: physics
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 the motion of an object" (change being the key word). If I had to choose one definition of force, it would be something like this:
Posted by Rhett Allain at 8:26 AM • 2 Comments • 0 TrackBacks
September 25, 2008
Category: physics
In a previous post, 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...
Posted by Rhett Allain at 10:40 AM • 0 Comments • 0 TrackBacks
September 24, 2008
Category: physics
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 are on a train that is moving 10 m/s to the right and you throw a ball at 5 m/s to the right. How fast would someone on the ground see this ball? You can likely come up with an answer of 15 m/s - that wasn't so hard right? But let me draw a picture of this situation:
Posted by Rhett Allain at 9:19 AM • 5 Comments • 0 TrackBacks
September 23, 2008
Category: physics
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 is no air in space. This is why they claim there is no gravity on the moon (even though there is - more on this later).
Posted by Rhett Allain at 10:02 AM • 8 Comments • 0 TrackBacks
September 21, 2008
Category: physics
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 are doing, you can cause some damage (much like flying a 747 after reading a blog about it). Speadsheets allow you to do a couple of things.
Posted by Rhett Allain at 8:16 PM • 5 Comments • 2 TrackBacks
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