I was looking back through old posts and many of them did not make sense. Apparently, RapidWeaver cut off the summary. I will go back and fix as many of these as I can. Curse you RapidWeaver.

Tags: rant

I have been using RapidWeaver to create all my posts on dotphys.net. RapidWeaver is a software package for Mac OS X that really does a good job. However, I think I have outgrown this and it is time to move to something else. New posts will be at http://blog.dotphys.net - this is a WordPress installation. Maybe you don’t care about these details, but maybe you do. Here are some reasons that RapidWeaver doesn’t fit anymore:

• It takes FOREVER to upload. Since RapidWeaver recreates all the menus on each page when a new post is created, the whole site gets re-uploaded for a new post. This was fine at first, but now that I have tons of posts, it is way too slow. I am too impatient to wait.
• I was never fully pleased with the site search that I implemented. WordPress has a built in site search. I think this is important with such a large collection of stuff (I sure like the word ‘stuff’), people (meaning my Mom) should be able to find it.
• WordPress is a pretty standard content management system for blogging, so there are many plugins available and lots of support (although rapidweaver also has good support).
• The comment system I use on RapidWeaver has never felt like it was good. Well, I guess maybe that is because no one ever commented on anything.
• RapidWeaver doesn’t come with a figure and you can’t take it in the tub. I don’t know why they changed it.

In order to keep my ties to the past, I am leaving this site as it is. I will continue to put some stuff on here, if it is of a longer nature (like my astronomy video lectures).

I have some comments about college life and learning. There are two things that seeded these ideas. First is this article from the Wall Street Journal - For Most People College is a Waste of Time. The second is this great essay on math education by Paul Lockhart - this is not the first place I found this article, but I can’t find the other blog that linked to it. Maybe you should read these two articles and then continue here.
Read More...

Tags: rant

Yes, this blog is mostly about science and physics stuff. However, I just wanted to give a couple of comments about diving the Oriskany (I am sure there is some physics in here somewhere). Read More...

Physics of Sustainable Energy: Using Energy Efficiently and Producing It Renewably - AIP Conference proceedings

Do you like talking about energy? Cars? Alternative and renewable energy? Need more info? This looks like a good place to start. This is the presentations from the AIP-APS-AAPT forum on Energy stuff.

Physics of Sustainable Energy Presentations (both pdf and powerpoint)

I looked through some of these and there are some interesting graphs I might come back to in the near future. You might want to bookmark this page or something.

Tags: energy

(How to make your own fake moon videos - or how to undo the fake studio videos)

Stop. Don’t say it. I know the moon landings were real, but I am just trying to have fun.

Some claim that the Apollo moon landings were faked in a studio. One way to make fake films would be to film astronauts and then slow the film down so it looks like they are on the moon. If this were the case, I could speed the videos back up to “normal” speed and see what they look like. After that, I will take normal videos and slow them down to make them look like they are on the moon.
Read More...

Tags: kinematics, gravity, video, fake, units

Starting Assumptions (estimations)
How many drive-throughs are there in the U.S.A.? When I think of drive-throughs, I think of McDonalds. Wikipedia says there are 31,000 restaurants world wide. I am going to say there are around 20,000 in the U.S. that have drive-throughs. So then, how many total drive-throughs? In my town, there are two McDonalds and probably 8 other major drive-throughs (Wendy’s, Burger King, Taco Bell etc....). This will give an extremely rough estimate of 100,000 drive-throughs in the U.S. (drive-through fast food).

There are also other kinds of drive-throughs. Drive-through banks, starbucks, pharmacy, liquor (yes, they exist). All of these will have different times, so I will first just deal with the fast food drive-throughs.

How many cars go through the drive-through a day and how long do they idle? I am going to estimate that the average over 8 hours a day is 2 cars in the drive-through line with an average wait time of 2 minutes. Yes, at lunch time there is a longer line, but sometimes there is no line. This is my estimation and I am sticking to it.

Calculating the hours of idle time
From this, I can calculate the average idle time. If there are 100,000 drive-throughs and for 8 hours there are two cars idling (I guess the wait time does not matter), that would be 1,600,000 idle-hours per day (100,000 x 8 hours x 2 cars). How much fuel does this use? Anecdotal claims from the internets say that cars use around 0.3 gallons per hour idling (I would have guessed higher than this). For this calculation, I will use 0.25 gallons of gas per hour idling. So, the total fuel per day wasted in drive-through (just restaurants) would be: 400,000 gallons.

Comparing to the U.S. oil used per day
Now to compare this to the 20 million barrels of oil used per day. 1 barrel of oil produces about 20 gallons of gasoline. So 400,000 gallons of gas saved would be 20,000 barrels of oil saved. This is just 0.1% of the oil used per day. Not nearly as much as the claimed 3% savings from tire pressure (although that is for people that don’t already have properly inflated tires). Also, that 3% is for individual savings, not for the whole nation.

Slow Down
I still think the best way to save oil is to drive slower.

Either way, the real issue is (as stated in the time article) how much would we get from off shore drilling? How much can we save by changing stuff.

Tags: energy

In this post, I am going to talk about real and not real forces as well as the fake centrifugal force (if you don’t like the word “fake” you could replace that with “fictitious”)

First, an example: suppose you are in a car at rest and press the gas pedal all the way down causing the car to accelerate. What does this feel like? If I weren’t skilled in the art of physics, I might draw a diagram something like this:

Yes, maybe someone would add gravity and the chair pushing up, but this shows the important points. What is this force of acceleration? What causes this? This is EXACTLY the same thing as centrifugal force. If you think centrifugal force is real, this also should be real. I think this is enough discussion to show that this force (and centrifugal) is not real, but I will continue. There is another mystery: why does it feel like there is a force pushing you back when you accelerate? (if you have read all my blog posts, you may have a hint to the answer).

Let me replace the person with a model of a person. Here is my model (very simplistic)

In this model of a person, there are 4 masses each connect to the adjacent “atoms” with a spring (I represent the springs as rectangles because of my laziness). Now suppose I push on this model from both sides with equal forces.

I put these big bars on the side to make it clear the force was applied to both “atoms” on that side. So, when these two forces are applied, 1) the object stays at rest and 2) the horizontal springs are compressed.

Now what if I just apply 1 of these forces:

Notice that the compression is EXACTLY the same before (Eye-dentical). Hey wait! How do I know that this one force would compress this exactly the same? Well, you or I could easily model this and in fact I have done so for a previous article (weightlessness and gravity)

If the above model looks the same, it means a person would feel the same. The only difference is that this person would be accelerating. The point of this story is that when a person accelerates, it FEELS like a force is pushing on you in the opposite way. One note: when you accelerate, it doesn’t feel exactly the same as if someone was pushing on you. When someone pushes on you, they are exerting a force on just part of you. When you accelerate, it feels like something is pulling on ALL of you.

Ok, now on to circular motion and centrifugal force. In the above case, what if I took a “picture” of the velocity vector after 1 second? The two vectors would look like this:

And using the definition of acceleration:

I can find the direction of the acceleration by finding the change in the two velocity vectors:

Ok, so maybe we are all happy with this? (I am happy) Let me move to circular motion. I will once again “take a picture” of the velocity vectors for an object moving in a circle.

Now, I can do the same thing as before to find the direction of the acceleration. (it is ok to move a vector as long as you don’t change its direction or length)

Key points: 1) the velocity did change (although only in direction and not in magnitude). 2) This change in velocity means the object accelerated. 3) in this case, the acceleration is towards the center of the circle.

This would make it “feel” like a force is pushing outwards. It is this force that people call centrifugal force.

Whenever one is thinking about forces, it is important to realize that forces are an interaction between two objects and there are only a few real forces. They are:

• Gravity - an interaction between objects with mass
• Electromagnetic - an interaction between objects with electrical charge
• Strong nuclear - an interaction between hadrons (protons and neutrons are two examples of hadrons)
• Weak nuclear - an interaction between quarks and leptons

Anything that is a real force should be one of these. Gravity is an easy one to pick out. What about me pushing on a book? That would be the electromagnetic force because the atoms in my hand are interacting with the atoms in the book (and that is what prevents my hand from going through the book).
What about centrifugal force? What are the objects that are interacting? (hmmmm.....) Which of the fundamental forces is it? (hmmmm.....). Well, it must not be a real force.

Don’t get me wrong, sometimes the idea of a centrifugal force is useful, but that does not make it real.

Tags: astronomy, forces, circular motion

Can you believe it? Have you seen this video?


Are you thinking what I am thinking? WOW. How could these people not follow my rules for cool internet video. Once again, here they are:

1. Keep the camera stationary. This way I don’t have to keep moving the origin in the movie.
2. Don’t Zoom. Same reason, this video followed that rule.
3. Include a clear and obvious calibration object. A meter stick would work, or even a Kobe Bryant (I can look up his height). Maybe it could be a Ford F-150 that has a known length. Something!
4. Include the mass and height of all people involved.
5. Use high quality video.
6. Don’t talk about fight club - oh wait, wrong list.

Despite failure to follow all these rules, I have managed to analyze this video. Really when I saw it, I said “wow” - was that real? It looked real, but who would get shot up that high? (it is on break.com, so fake is a possibility).
Read More...

Tags: kinematics, video, energy

I am always looking for videos to analyze. Here is a site with many high speed videos. The clips seems to be in low resolution and in Windows Media Format, but still looks like there are some good ones.

High Speed Videos (Dr. David Alciatore at Colorado State University)

Tags: video

I could make a way to pretend this is physics, but really it’s just funny.

Here is a picture a friend of mine took of the Chicago Tribune with his phone while he was walking to work.

I have tried to talk about energy and perpetual motion machines before (and how they can’t work). Surprisingly, people keep coming up with ideas about energy creation that just shouldn’t work.

http://www.lhup.edu/~dsimanek/museum/physgal.htm

This site is very comprehensive in covering the different ways people make mistakes about perpetual motion machines. Great examples also.

Tags: energy

I must have previously mentioned my online lectures (mini-lectures) in astronomy. Well, I got quite behind in my postings. In an effort to complete the semester, I have added some more videos - namely

• Doppler effect
• Blackbody radiation
• Telescopes
• Introduction to the terrestrial planets

I posted all these videos on Vimeo - but you can find links and descriptions here

Tags: astronomy

So, here is a video (from break.com - so you know it is likely fake).

Extreme Catapulting - Watch more free videos
If for some reason, you can not view this video, here is the plot.
1) Guy wears parachute and brings a portable thing like a see-saw.
2) Guy approaches large crane dropping a large mass repeatedly (I assume to flatten a dirt road)
3) Guy sneaks up an puts the see-saw under the area that the mass drops on and then stands on the other end of the see-saw.
4) Mass drops, guy shoots up and parachutes down. Read More...

Tags: forces, video, fake, energy

I usually create posts focused on physics and science stuff, but I like to talk about learning also. Today I will talk about the question that comes up with faculty. Should you have attendance count as part of the course grade?
Read More...

Tags: teaching, lecture, attendance, rant

So, I always try to get on Digg (a social content system) - specifically to promote my stuff. Anyway, Digg introduced a new recommendation engine. The basic idea is to find submitted stories similar to stories that a user has “dugg”.
Read More...

I have been thinking about gasoline (I can’t help it). In an effort to show my students different energy sources, I realized the power of gasoline. There is a reason we have an oil-based energy system, its cheap (still cheap comparitively) and it has lots of energy. Yes, we need to move past oil that is clear. Yes, fossil fuels lead to pollution and green house gases. But still, it is important to realize why we are here.
Read More...

Tags: gas, energy

I often have a discussion with students about science. It usually starts with a student claiming that they really aren’t a “science person” they are more of a “___________” person. (where the blank can be english, history, art, etc). There are several important things about “I am not a science person”, but today I would like to compare science and history because really, they are not that different.
Read More...

You see this all the time in textbooks:

This is often described as “the acceleration due to gravity”. Is this really the best thing to call this? No. A better name would be “the local gravitational field” and list it in units of:

Read More...

Tags: gravity, kinematics, forces

• Moon Landing Theory. This is the theory that in 1969 people ACTUALLY landed on the moon. There are many people that claim this did not actually happen. Both sides of this argument should be discussed. Here is a good place to start - (Bad Astronomy)
• Global Warming Theory. Some claim that the Earth is in a warming trend and that this trend is caused by human activity. Of course, this is just a theory. Another theory is that global warming is directly correlated with the number of pirates in the world. Here is an article on the relationship between temperature and pirates (see - its a real theory)
• Flying Spaghetti Monster Theory. Really, this one isn’t as much a theory as it is a FACT. This is the notion that there is a flying spaghetti monster that does stuff. It is not really considered a theory becuase it is in wikipedia, the source of all truthiness.
• Oblate Spheriod Earth Theory. Many textbooks descirbe the Earth as a sphere, or better as an oblate spheriod. This really neglects the whole other side of the debate about the shape of the Earth. For information about the Flat Earth Theory - see the online stuff.
• Light Wave-Particle Duality Theory. ALL textbooks in physics talk about light being both a wave and a particle. Why? Well, it seems that Einstien sort of suggested this as an explanation to the photoelectric effect. It turns out that the photoelectric effect can be explained with classical wave theory and a quantum theory of matter.
• Hydrino Theory. This theory claims that hydrogen energy states can lowered past the accepted ground state value hinting at near unlimited energy possibilities. Of course, there is no experimental evidence to support this theory, nonetheless it should still be debated just like the theory of evolution.

I know I left off some great theories that should be debated, but I just can’t think any more. If you are a Louisiana teacher, feel free to contact me if you need materials to debate these theories in your class.

Really, don’t think of the LA Science Act as a limitation but more as an opportunity. Also, with great power, comes a greater responsibility to do good.

Tags: fake

So how much would be enough to be useful? I am going to ballpark 500 Watts (although certainly less could also be useful). What kind of flow rate would one need to get this? I will assume some type of stream where someone could produce a 1-meter vertical drop.


How much energy would you get from moving a mass of water m down 1 meter? The change in gravitational energy of a mass of water would be:

Suppose I want 500 Watts, that would be 500 Joules/sec. Suppose also I have 1 kg “pieces” of water. Each piece would give 9.8 Joules (at best). So how many of these pieces of this water would I need each second? I would need 500/9.8 = 51 pieces per second. This would give a flow rate of:

Of course this assumes 100% conversion from gravitational energy to electric energy. Clearly that is not going to happen. If I assume a 50% efficiency, then I would need a flow rate twice that - 102 kg/sec.

Suppose all this water was coming through a pipe, how fast would it have to go? If I have a 1 inch pipe, then I would need to first look at the volume flow rate.
Assuming water with a density of 1000 kg/m³ then the flow rate would be:


How fast would the water have to flow to get this?

How long would this pipe have to be to get 0.051 m³?
Well, the cross sectional area would be:

So, if the volume = 0.051 m³ then the length would be:

If all of this moves through in a second, that would make a flow speed of 100.6 m/s or 225 mph. Seems kind of fast.

Tags: energy

Ok, I this just came up and I had to write something about it (even though I have tons of other things to do). Here is a video of a guy jumping 35 feet into a pool of water only 1 foot deep.

How does this work? Read More...

Tags: acceleration, video, gravity, energy

I am really not sure why I started to look at this, but here is a video of the famous “jump salute” from Apollo 16 astronaut John Young.

It seems there is some discussion about this video in terms of fake or not fake moon landings. I don’t want to get involved in that whole mess, so I will just see if I can measure the gravitational field on the moon. Read More...

Tags: video, acceleration, gravity

I like demos. They are kind of like magic tricks, but you get to explain something also. I recorded this demo and I was going to use it for my astronomy lectures, but it just didin’t fit in anywhere. I recorded this demo, but my kids were making a lot of noise, so I re-recorded the audio. Didn’t quite turn out like I wanted. Here is the video:

Inertial demo from Rhett Allain on Vimeo. Read More...

Tags: forces

I am currently teaching an introductory astronomy course for non-science majors. I thought this might be an opportunity to turn this into something useful. Why not just put my lectures online? Well, instead of actual lectures, I created presentations with voice overs. Read More...

Tags: astronomy, video

I really have other work to do, but this is fun. Spoiler ALERT!!!! If you have not looked at the car talk puzzler of the week, maybe you should avert your eyes. Really, this one is not nearly as hard as some of the others. The basic idea is that a couple drives from LA to Monterey. On the way back they take their time and leave at a different time. What is the probability that they are at the same point on the trip at the same time? Read More...

Tags: velocity

We have all seen the Kobe Bryant video of him jumping over an Aston Martin - this keeps coming up on the Internet. There has been vast discussions of whether this is real or fake. I will do my best to examine the evidence. In short (in case you don’t want to read the whole thing) Kobe can most likely really jump that high, it is possible that there was some perspective trickery involved. Here is the video in case you are brand new to the WWW:
Read More...

Tags: kinematics

Sometimes it takes an article to inspire me. I just read an article about Dale Earnhardt Jr using pulse-and-glide techniques in NASCAR and it got me to thinking. The basic idea of pulse and glide (as I understand it) is to not use your engine as much when it is at a low load because it is not as efficient. Instead, accelerate to 10 mph over your desired speed and coast to 10 mph under your speed limit. Apparently, this can save fuel.
Here is the question: How do you drive to make your average desired speed? Read More...

Tags: speed, velocity

I see alternative ideas about powering cars on the internet all the time (as you probably do also). The latest is a car that runs off of water from Japan. My problem has always been “where does the energy come from?” If you use water as an energy source, you would have to reduce its energy somehow. Not sure how you would do that. Robert Rapier has done a little investigation and found that the car likely uses metal hydrides to release hydrogen from the water.

Read his post, it includes a good explanation.
Read More...

Tags: energy

So, I am teaching a class. I do this quite often. One thing I noticed is that some students are very concerned about missing class, but they don’t do too much work outside of class. For me, class is like the tip of an iceberg.

Read More...

I like to ride my bicycle. I like to ride it well. I ride it to work whenever I can. I think this is a good thing and not one bad thing about it. However, occassionaly I will have someone in a car yell at me. It usually goes something like this:

“Get of the silly road you person”

But occasionally they will say things a little more colorful. But the question remains. Should I instead ride on the sidewalk?


Read More...

Tags: rant, bike, energy, momentum

I use the following analogy quite often. Usually, this comes up when I talk to students about how to succeed in class. The problem is that some students have an idea about learning that goes like this:


Read More...

So, you probably didn’t notice (unless you are one of the two people that consistently read my blog - Hi Mom!), but I moved around and cleaned up my categories. I also added tags. The idea is that you can find topics related to a particular concept in physics - like momentum or what not.

There are some other changes. Read More...

This is a surprisingly fun question to ask.

Which of the following is the farthest from the Earth?

1. The Moon
2. The Sun
3. Jupiter
4. A star

Read More...

Tags: astronomy, question

I was at my parents house and I found this:

My Dad said I could keep it. This is so awesome. Reverse Polish and everything. Read More...

Tags: HP

On my dive to school today, the Walton and Johnson show was on. I think the topic of complaint was off shore oil rigs. One girl (lady) called in and said something along the lines of:

“Let me give you guys a science lesson. The human eye can only see 17 miles. So, if they put oil rigs more than 17 miles off the coast, no one can see them to complain about them.”

So, why did I think this was interesting?
Read More...

Tags: light

Tom, Ray, I still think you are Awesome
However, your physics seems to be incorrect.
In CarTalk episode #0821 the car talk guys take a caller with a physics question. "How does a car crashing into an immovable wall compare to a car crashing into another similar car going in the opposite direction?" This is the basic question. Tom and Ray claim that a car crashing into an immovable wall going 120 mph is equivalent to two cars going 60 mph crashing head on. Read More...

Tags: work, energy

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. Read More...

Tags: energy, cars

I try to stress to people that driving faster on shorter trips doesn't really make THAT big of a difference in time. Also, you can save money by driving slower. This was essentially the idea behind my optimal commuting speed calculator. The problem is that this calculator doesn't really work if you don't get paid by the hour. I decided to make a graph anyway that shows the decrease in your efficiency (and thus increase and how much you spend on gas) at the same time showing how much time you save. That way, you can use your own weighting of the importance of time.

For this graph, I used an efficiency of 25 miles per gallon when driving 70 mph. The trip distance is 20 miles and the cost of gas is $4 per gallon.

You can see going 90 mph instead of 50 mph save you 10 minutes, but cost more than $2.50 dollars MORE than going 50 mph.

Tags: energy, cars

Ok, I am trying to be quick with this, since it is current. Here is an awesome video of Kobe Bryant jumping over a pool with snakes in it (I found this on digg):


It looks so crazy, I wanted to do a quick analysis to see if this is feasible (well, I know it is not feasible for me). Let me just pull out one of my favorite tools - Tracker Video Analysis. Read More...

Tags: fake, kinematics, video

Read More...

Tags: energy, cars

I am sure that I have mentioned Plot before (Free plotting program at http://plot.micw.eu/). Well, it sure makes shiny looking plots, but I have had trouble getting started with it from time to time. I almost abandoned using it for something with a larger user base like GNUPlot. For some reason, Plot does not have tons of documentation and I did not find a forum of users that discussed Plot (and I am afraid to email the developer). So, when I finally figure things out, I think I will post them.

UPDATE: I forgot to mention why this is a problem. The root of the problem is the name of the program - plot. How am I supposed to search for help on the program Plot? Not a good googlized name. He should have named it macplot or iplot or plott, or plot-o-lama-ding-dong. That would have been easier to search for. That is why I have explicitly included the website on this page. Oh, this is Plott 0.997 (the Mac OS plotting software). Hope that helps future searchers.
Read More...

Tags: graphing

Everyone is concerned about power and carbon dioxide, right? Well, maybe we should look at some alternative energy sources. I previously proposed using the rotation energy of the Earth, but that didn't go over too well with the internet community. How about people power?

Can people be used to produce power? Obviously. Do people produce carbon dioxide? Sure, its called breathing. Would we do better to use people? I don't know, but I will try to make some simple calculations. Read More...

Tags: energy, cars

Here is a nice little (well not too short) quiz on the basics of high school level physics (with no math). Basically it is a true or false type quiz. Take it for fun:
Physics Savvy Quiz
I missed a couple of the questions (well, technically I missed three).

One question was about negative acceleration. I really don't like this because I think of acceleration as a vector:

In which case "negative" acceleration does not really make sense. If you are talking about components of acceleration, then you can have a negative component. It is possible to have a negative component of acceleration in the same direction as the component of velocity, so that would make the speed increase. I guess I am just sensitive about vectors. (really I am just making an excuse for why I missed that one).

The other one I missed was comparing milliliters and cubic centimeters. I never see milliliters and accidentally read it as millimeters. You can't compare millimeters and cm³, so I chose false. That is wrong.

The last one I missed is completely my fault. It was asking about the mass of a cloud. Really, just a lack of knowledge on my part.

Anyway, check out the quiz. Lots of fun. Really, I am just stalling because I have not finished my next project and I don't want to leave my site unupdated (I know thats not really a word).

Tags: kinematics

So, you knew I was going to make some mistakes on the physics of scooting - right? I don't think these mistakes are major and they don't take away from the main idea. Read More...

Tags: forces, kinematics, modeling, momentum

There you are, in your rolling chair. You need that extra pencil, it is just a few feet away but out of reach. For some reason, you don't want to touch your feet to the floor. How do you get that pencil? You scoot. Still don't get it? Here is an example:

Why do people scoot? I don't know. My kids do it too. When does a human learn to scoot? How does a scoot work? Really, I am just going to answer that last question, but the others are interesting also. Read More...

Tags: forces, kinematics, modeling, momentum

I like numerical calculations. I think they are useful. But what should I use to create my calculations in? I am still not sure. Here are my options:

• VPython: I think this is the easiest for me to create things in. Python is uber-simple and the visual module has most of what I want. VPython 4 is currently in development and will run in Mac OS X without using X11 - so that is good. One bad thing about vpython is that it seems a little slower than java. I could be wrong about that though. The other big problem with vpython is the question of how to share simulations. It would be great if you could embed vpython in a webpage, but you can't. A user would have to download the code, install vpython and run it. This is ok if one is using it for courses, but not if you want a more general audience to look at it. Oh, vpython is free. One more thing, I feel comfortable creating stuff in vpython.
• Java. On its own, I probably wouldn't consider this. However, there is opensource physics. Opensource physics is a set of java "stuff" that allows you to create java calculations without doing all the crazy (programming) stuff. You still have to compile the programs, but it gets a lot of the difficult stuff out of the way. This stuff looks pretty powerful, but with great power comes a greater responsibility to do good, and I am just not sure I can do good. Really the problem is that java is pretty darn complicated compared to vpython. I can crank out some pretty simple stuff in vpython WAY quicker than in java. On the plus side, java is free AND you can make apps that can be run from the web, so a user would only need to have java installed - many do have this.
• Flash: Flash is pretty with its vector-based graphics. Also, I am told it can do many of the things java can do. But to tell you the truth, I really don't "get it". What Josh, what don't you get? So, its a robot that turns into a building? What's fun about that? I tried making a simple program, but there are too many new terms that just plain confuse me. Another problem is that this sucker is not free, nor cheap. I have a friend that is big into flash, he keeps telling me I can get into it fairly quickly. So the two big pluses are - it looks good, runs in web pages. But it is not free. If I get into flash and I want students to do flash stuff, they can't because they won't have it. Also, what is AIR? Is that free? I never figured out what air is.
• M.S. Excel. What? Are you kidding? This is a great tool for basic calculations and a great way to involve students, but I can't stand using spreadsheets for calculations. I hate highlighting cells and graphing and all that stuff. Yes, there are some great free spreadsheets, but for me I will not use them for this stuff.

So that is where I am. Stuck.

Tags: modeling, numerical , computer

The following is an article written by David Norwood. He submitted this to some online journal, but it was never published (as far as we can tell). Here is the article.

The effect upon global temperature of talking like a pirate
David Norwood, Ph.D. scientist, FotLCoP
Fellow of the Louisiana College of Pastafarianism
My House

Abstract
It is well established with a graph that global warming is caused by a pirate deficiency
[Henderson, 2005]. We prove scientifically, with a graph (including error bars) and
references, that the precepts of Flying Spaghetti Monsterism are true and that anyone who
doubts them is wrong.

Read More...

Tags: fsm

I mentioned this previously, but this came up again. Here is a diagram from a resource letter on computational physics:

The idea represented is that somehow simulations are different than theory and experiment. Read on for my response to the editor. I am posting it here because I doubt it will be published.
Read More...

Tags: numerical , computer

It looks like my bike learning method is working well (by my, I mean the one I use not the one I created). This weekend my 4.5 year old daughter successfully rode her bike without training wheels. The problem is that riding a bike is not easy, nor is it intuitive. When riding a bike, and you are falling to the left, what do you do? You TURN TO THE LEFT. What? That doesn't make any sense. That is why bikes are difficult, especially for kids.
Here is are my easy to follow steps. (I discuss some of the physics of bike riding that I looked up on the internet here) Read More...

Tags: bike

In case you never saw it, here is the part of the episode where the Mythbusters explode a water heater.

I started to analyze this previously, but it wasn't complete. Now I will finish what I started.

If you are curious, here are the "answers":
Time of flight = 11.8 seconds.
Max height = 167 meters = 548 feet
Speed on impact (ground) = 34 m/s = 76 mph (compared to 234 mph initially). Read More...

Tags: mythbusters, kinematics, video, air resistance

I just want to say that I really like computers. I like doing physics with computers. Its great, I can sit here and work on physics stuff at the same time as checking email and listening to music and stuff. Numerical calculations are awesome. I also see lots of people promoting computational physics, but there is a problem. A common way to pitch the idea of computational physics is to say its like a 3rd way to do physics, the three ways being:

• Theory
• Experiment
• Computation

I have a problem with this. Computation is not a third thing, instead it is a type of theoretical calculation.
Suppose I want to apply a model of a ball falling without air resistance. How could I study this? Here are some options:

• I could use Newtonian mechanics and integrate starting with F = ma (most people would call this theory)
• I could drop a ball and make a video of it falling. Using this I could get position and time data from the video. (most people would call this an experiment)
• I could also create a numerical calculation using VPython or Excel to generate the position of the ball at different times. (most people would call this computational physics) - It is fine with me to call this computational physics, but it is really no different than theory.

Theoretical physics takes some known model and calculates "stuff" from that model. This is exactly what computational physics does, but it does not use analytic tools like calculus, instead it uses a numerical tool.

The important thing to realize is the starting and ending points for theoretical and computational are the same. Computational is definitely NOT experimental physics.

Tags: numerical , computer

It appears my training has been successful. My son spent a year using training wheels and could never make the transition to no-training wheels. With the no-pedals method, he spent a week pushing and gliding on the bike. Yesterday I put pedals back on and BOOM - he had no problem riding.

I am not saying training wheels are bad, no wait.. I am.

Tags: bike

PHOTON

This word comes up quite often in physics. What does it mean? What do people use it for? How did this word come about? Do we EVEN NEED this word? Surprisingly, the answer to the last question is NO. You can mostly blame Einstein, but also Gilbert Lewis on the Nobel Prize committee - whoever they are called.

(the following is a summary of arguments summarized by my colleague David Norwood - so you can argue with him when you do not agree with this).

Before I go further in my summary, here is the paper from Norwood that I am basing this post on - The Use and Abuse of the “photon” in Nanomechanics (pdf)

In case you don't like to read much, here is the whole point:

• Einstein's explanation of the photoelectric effect says that light is like a particle
• Gilbert Lewis comes up with the term "photon"
• Textbooks from thence forth use the concept of the particle nature of light
• It turns out that the wave nature of light explains the photoelectric effect (and many other effects that people use to proclaim photon-ness of light)
• There is perhaps a need for a quantum theory of radiation, but this is different than the particle-nature of light.

Read More...

Tags: photon, light

Suppose I want to have a lab activity with a dropping tennis ball. Do I need to worry about air resistance or can I assume there is none? This is a that was recently asked of me. Below is my answer: Read More...

Tags: forces, kinematics, numerical , computer, air resistance

One of my kids is behind in his learning to ride a bike. There are a couple of problems. First, the bike is just the right size (it should be way too small to learn on). The second problem is that training wheels don't really do much to help you learn to ride a bike. To assist in his learning process, I modified his bike in the following way:
Read More...

Tags: bike

I was recently re-watching a MythBusters episode and I found something I had wanted to explore previously (but accidentally deleted the episode). Here is a short clip from the "shooting fish in a barrel" episode:


Did you see what I found interesting? That big barrel of water left the floor from being hit by a bullet - here is a quick analysis Read More...

Tags: video, energy

I have posted an "online presentation" about weightlessness and gravity. This has taken some time to put together since I had to build some stuff (vomit comet for toys). Anyway, hopefully, you will find this helpful and useful.

Weightlessness and Gravity
Apparent Weight
Building a Vomit Comet Read More...