rallain | November 6, 2008I just watched two episodes of the discovery show [Time Warp](http://dsc.discovery.com/tv/time-warp/time-warp.html). Really an interesting show. There are many videos that I could see some analysis project for (too bad I am like 20 projects behind schedule - I think of things faster than I can do them). There is one problem though. It seems like all of the people on the show like to use physics terms, but they use them incorrectly. This DRIVES ME NUTS. You can't have "energy going this way". Energy is a scalar, not a vector. You can't have "force flowing through this". You can't "put…
rallain | November 5, 2008[Here is a LiveScience article on cars that run "mostly" on air](http://www.livescience.com/technology/081103-air-car.html). I also hear students talking about this - how the world will change when cars run on air. This is misleading. These cars do not really run on air. It is not like you put them outside and BOOM - instant energy.
A better way to say this is that these cars run on energy STORED in compressed air. How do you store energy in compressed air? You need a compressor that typically runs on electricity. Where does that energy come from? Probably coal or natural gas.
It…
rallain | November 4, 2008**Pre Reqs:** [Work-Energy](http://scienceblogs.com/dotphysics/2008/10/basics-work-energy.php)
You need to be familiar with work and energy to understand this. If you are not familiar, look at the pre requisite link. Ok? Now, let's begin.
Suppose a ball moves from point A (3 m, 3 m) to B (1 m, 1 m) at a constant speed as shown in the diagram below:
Suppose there is some other force (like my hand) also exerting a force on this ball to make it move along this path at a constant speed. What is the work…
rallain | November 1, 2008I have been meaning to post something useful lately, but I am currently at the southeastern section of the APS. Anyway, I saw [this link on digg](http://www.hyperevo.com/new%20site/index.php?subaction=showfull&id=1225…)
Apparently there is a message in the source code on the digg page. Funny stuff.
rallain | October 29, 2008I don't need to explain that I think the Mythbusters are awesome (do I?). I just finished watching their latest episode. In it, they tested the scene from Indiana Jones and the Last Crusade where Indy puts a flag pole in another motorcycle wheel. The result in the movie is that the motorcycle goes flipping in the air. I have no problems with their test - it seems like they did a decent job. However, in the end, Adam says something to the effect:
*"Look how high that bike went. It took a lot of energy. There is no way that energy could come from this stick I shove into the wheel."*
I am…
rallain | October 28, 2008Yes, I did some experiments with [Fantastic Contraption](http://fantasticcontraption.com/) ([Water sticks in Fantastic Contraption](http://blog.dotphys.net/2008/10/water-stick-springs-in-fantastic-contra…), [Torque from rotating balls in FC](http://blog.dotphys.net/2008/10/torque-produced-by-balls-in-fantastic-c…), [Basic stuff in FC](http://blog.dotphys.net/2008/10/physics-of-fantastic-contraption-i/)). But apparently, there is a wiki with some of the answers:
[List of physics parameters for Fantastic Contraption](http://fc.therisenrealm.com/wiki/List_of_physics_parameters) I assume these…
rallain | October 28, 2008Here is what is cool about [Fantastic Contraption](http://fantasticcontraption.com/) - it's like a whole new world, a world ready for exploring. I am Newton, and I can see if this world follows the models that I propose.
In this post, I am going to explore the elastic nature of the "water-sticks". If you have played fantastic contraption, I am sure you noticed that the water-sticks are springy. How does these springy sticks work? Are they just like the springs we have in the real world? An excellent model for springs in the real world is Hooke's law. It says the force exerted by a…
rallain | October 26, 2008The fun part about exploring the physics of [Fantastic Contraption](http://fantasticcontraption.com/) is coming up with new setups to test ideas. Torque is not too difficult to set up. Here is what I did:
In this setup, I have a "turning ball" with a wood stick attached to the side. I increased the length of the stick until the ball does not turn. At this point, the torque from the gravitational force on the stick is equal to the torque from the ball. I can use [Tracker Video Analysis](http://www.…
rallain | October 23, 2008One of my students showed me this game, [Fantastic Contraption](http://fantasticcontraption.com/). The basic idea is to use a couple of different "machine" parts to build something that will move an object into a target area. Not a bad game. But what do I do when I look at a game? I think - hey! I wonder what kind of physics this "world" uses. This is very similar to [my analysis of the game Line Rider](http://scienceblogs.com/dotphysics/2008/09/the-physics-of-linerider/) except completely different.
Fantastic Contraption gives the unique opportunity to build whatever you want. This…
rallain | October 23, 2008I am sorry to point this out, but I can't help it. My kids watch this show "Fetch with Ruff Ruffman". It's mostly an ok kids show. However, there was a problem. In one episode, some kids were in the desert and measuring temperature with (they said it several times and it was even a quiz question at the end) - a LASER. Here is the device they used:
This is an infrared thermometer with a LASER aiming system. The laser is only there to help you aim. The temperature is determined by measuring the infrared…
rallain | October 21, 2008[In a previous post, I talked about numerical calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…). The basic idea is to use the momentum principle and the following "recipe":
Update the position of the particle
Update the momentum of the particle
Update the force on the particle
Looks great, right? Well, it mostly is great. I want to give a couple of pointers about the last step, update the force on the particle. How and when can you do this? Really, in numerical calculations, you will see two types of forces:
Forces that you can calculate: That looks…
rallain | October 21, 2008I know I should just let go, but this is what makes me, me. I understand that there are terms in physics (like for instance 'pressure') that are used in all sorts of ways in common language. The problem is when someone tries to explain something scientifically and misuses a word. Pressure means something. It is the average force per area due to collisions of a gas or liquid on a surface. Really, you can see a good animation of this, I have a link and explanation when [I talked about MythBuster's Lead Balloon](http://scienceblogs.com/dotphysics/2008/09/mythbusters-how-small-could-…).
So,…
rallain | October 20, 2008**Pre Reqs:** [What is a Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
[Previously, I talked about the momentum principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…). Very useful and very fundamental idea. The other big (and useful) idea in introductory physics is the work-energy theorem. Really, with work-energy and momentum principle, you will be like a Jedi with a lightsaber and The Force - extremely powerful.
Well, what is work? What is energy? How are they related? In [another post, I talked about energy.](http://…
rallain | October 17, 2008This is not a "fix-it" blog. However, I think the Internet should be a useful friendly place. Think about the times you have had a problem. The Internet has been there for you - right? I remember not too long ago, I was trying to set up iChat video chat with my brother-in-law and his brand new iMac. I was 3 states away and it was getting frustrated. In the end, my friend the Internet helped me. Problem solved. Everyone one has found a perfect solution for a particular problem on the Internet - right? So, this bud's for you Mr. Post-obscure-stuff-in-the-hopes-that-at-least-one-person-…
rallain | October 16, 2008Maybe you know I like numerical calculations, well I do. I think they are swell. [VPython](http://vpython.org) is my tool of choice. In the post [Basics: Numerical Calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…) I used vpython and excel to do something simple. I will do that again today (in that this problem could also be solved analytically). However, there is one big difference. This problem has a non-constant forces. Suppose I have a mass that is connected by a spring to a wall. This mass-spring is sitting on a table with no friction.
, [Momentum Principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…)
What are "numerical calculations"? Why are they in the "basics"? I will give you really brief answer and then a more detailed answer. Numerical calculations (also called many other things - like computational physics) takes a problem and breaks into a WHOLE bunch of smaller easier problems. This is great for computers ([or a whole bunch of 8th graders](http://scienceblogs.com/dotphysics/2008/09/…
rallain | October 13, 2008I went home for lunch today. While waiting, I saw this lizard. We have many lizards in Louisiana, I like them, really I do. So, this is what I did:
No lizards were harmed in the filming of this video.
I was really surprised. I thought for sure that I had tried this before and nothing happened. Maybe it was because of the white surface the lizard was on. Maybe it was because it was an older and wiser lizard (it was larger than normal). Maybe this is already a well known fact about lizards and laser pointers. Needless to say, this was quite entertaining and completely justifies the…
rallain | October 13, 2008There is this show "Weapon Masters" - I think it comes on the discovery channel. It is not a bad show. The basic idea is that they have this history guy talk about the historical aspect of some type of weapon and this other guy tries to make an improved version. Last night the goal was to recreate the original flame thrower mounted on a boat.
They found a boat and they needed to test it's sea worthiness. The builder guy (sorry, I don't know his name) estimated that they would have 1000 lbs of equipment in the boat. To simulate this weight, they put 4 guys and two barrels of water in…
rallain | October 9, 2008**Pre reqs:** [Free Body Diagrams](http://scienceblogs.com/dotphysics/2008/09/basics-free-body-diagrams.php), [Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
The time has come to look at things that are NOT in equilibrium. The most basic question to ask yourself is: *"What do forces do to an object"*? Aristotle would say that forces make things move. Constant forces make things move constantly. Actually, Aristotle said there were two types of motion:
Natural motions: These motions don't need anything to happen, they just do. Example: a rock falling. You…
rallain | October 9, 2008Dear Mythbusters. I hope you know that I think you are awesome. I know you are not scientists, but rather master robot builders. I respect that. I envy your robot-building abilities. Please forgive me for pointing this out - but even if a tree is 90% air, that does not mean a ball has a 90% probability of passing through it.
For those of you who are unaware, in the last episode of MythBusters, they explored the idea that a golf ball should pass through a tree 90% of the time. What if they were to test following alternative myth:
*A golf ball has a 90% chance of passing through something…