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

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

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

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 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 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

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

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

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 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

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

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...

Tags: video, gravity

I don't know why I even suggest a new energy source. Fusion power is only a few years away in the future (just like it as always been). This will replace any other sources of energy that we could come up with. But, I can't help myself, I need to share my idea and save the world. Its what I do. (call me a superhero is you want).

We can get all of our energy from the rotation of the Earth. Read More...

Tags: energy

Some time ago, I posted an analysis of the Ford F-150 commercial where the truck is shown to stop a landing C-123 Airplane. Apparently, this was quite popular and I received some useful and interesting feedback. From this, I have a few updates. Read More...

Tags: video, kinematics, forces, momentum

The normal force is a force exerted by a surface onto an object. There is some really cool things about this force, almost like it is magic. Read More...

Tags: forces

You may have seen this before as it was on my old server. It has recently been moved over to this server. In case you don't know what a numerical calculation is, let me give brief summary.

Suppose I throw a ball up in the air and I want to determine how long it is in the air. I could start with the kinematic equations for motion with a constant acceleration:
Solving this for time would be what I call an analytical solution (my terms might be slightly different than other peoples - but they can adjust). In an analytical solution, one basically starts with some expression and algebraically (or using differential equations) solve for an unknown variable. In this case, I could get y(t) - which would pretty much be more than you are looking for.

Now for Numerical calculations: Read More...

Tags: numerical , computer

First, I am not really sure why Newton got to call this HIS law. Second, its not really a law. What happens if you don't obey this law? Would I go to physics jail? Ok, now for the good stuff. I am going to try to give a brief summary of Newton's 2nd law. Read More...

Tags: kinematics, momentum, forces

Let me start with a story.

A guy calls me up in my office (this happens sometimes). He says he wants to know if he can run a car off of hydrogen. I tell him I imagine it is possible, but it probably wouldn't work too well. Here is his plan. He wants to have the engine run an system to break water into hydrogen and oxygen. The hydrogen will then be used back in the engine. Maybe you already see the problem with this situation, but many clearly don't see the problem. Let me draw a little diagram to help.
Read More...

Tags: energy

I think it is time for me to talk about energy. My ultimate goal is to give some insight into the many stories about perpetual motion. To do this, I will first talk about the fundamentals of energy. In part II, I will talk specifically about perpetual motion. Read More...

Tags: energy

Clearly, I find some joy in analyzing these Ford commercials. In the latest release, a F150 is spun around in a homemade centrifuge. Yes, this is an awesome opportunity to discuss physics, but is that Ford's intent? Ford is clearly trying to get a message out with this. The following screen shot shows the real message:

See that at the bottom? Closed centrifuge. Do not attempt. Damn you Ford! Why must you ruin my fun? Why do you think I have a centrifuge (an open centrifuge, btw)? Well, I guess all that is left is for me to analyze this commercial. (you can see the whole behind the scenes here - http://www.fordvehicles.com/f150behindthescenes/) Read More...

Tags: video, circular motion, forces, momentum

Aristotle: A constant force makes an object move at a constant speed.

Newton: A constant force makes an object move at a constant acceleration (changing velocity)
Read More...

Tags: forces, kinematics

When you open a switch (break the circuit) in a circuit, you will usually see a tiny spark. This is because there is inductance in the circuit so that you can't instantaneously change the current. Is it possible to open a switch with absolutely no spark? Clearly you can make a circuit with a non-noticeable spark. Read More...

Tags: electric current

So, you are taking a college science course. Maybe it is physics, maybe it is chemistry, maybe its a lab. Either way, you always end up with these problems that involve unit conversions. You think you have the hang of it, but sometimes you make some mistakes. Here is my explanation for converting units. Read More...

Tags: units

On this week's 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? Read More...

Tags: mythbusters, forces

I don't know who you are. I don't want to know. It has taken me all my life to figure out who I am, and I am tired. Do you hear me? Whoever you are, you might need to know something about vectors. What are they? What do you do with them? I will tell you in this short introduction (hopefully helpful). Really, this is just an introduction to adding vectors. Read More...

Tags: vector

Ford, why are you the way you are? Do you actually have people look at your commercials? Or do you just assume that you can say and show whatever you want and I will buy a truck? I am sorry, I shouldn't say that. I do enjoy analyzing your commercials - so, please continue.
Ford's latest F150 commercial shows a big thing dropping from a helicopter to the bed of an F150. The claim is that Ford is awesome. 30,000 lbs awesome. Let's check this out.
Read More...

Tags: video, modeling, momentum, forces, kinematics

Line Rider. Yes, its a game. Yes, I know its not real life. Nonetheless, I analyze what I see. How is the physics in line rider? Does it agree with Newtonian mechanics? What is the scale of the line rider? What other questions are there? What other questions are there? Read More...

Tags: forces, kinematics, momentum, energy

I am sure you have seen this commercial:

They say its a real demonstration, but it has seemed odd to me. (they also say this is a professional driver on a closed course and don't try this at home - damn! I was SO going to do that this weekend). Here is my analysis: Read More...

Tags: momentum, forces, kinematics