Statics: Still Hanging On... ...

We’ve been studying statics in our physics class. We have examined how to calculate the forces in ropes and cables that support hanging objects. Up to this point, we’ve only considered the cases where the cables are symmetric (make the same angle with the horizontal).

Consider (the somewhat unorthodox) case where a sign is hung by two cables that *are  not* symmetric—here, the cables each make different angles with the horizontal. Let’s do some work to calculate the force in each cable:

1. Suppose the sign’s mass is 5 kg. What is the weight of the sign?
2. Call the tension in the left cable F_L and the tension in the right cable F_R. Write an expression for F_Lx, F_Ly, F_Rx, and F_Ry.
3. Write an equation relating the forces in the vertical direction. (HINT: Think balanced.)
4. Write an equation relating the forces in the horizontal direction. (HINT: Think balanced.)
5. Notice you should now have two equations with two unknowns F_L and F_R. Solve the resulting system to find the tension in each cable.

Hurray for Snow!

This morning, we were greeted by a fresh blanket of snow. Unfortunately, it doesn't look like this snow will last very long. Temperatures are predicted to be well above freezing today. I wonder how long this snow will manage to stay on the ground before it melts... ... Can we use some basic physics formulas to predict?

To get started, we need to make a few assumptions:

1. Let's look at 1 square meter of ground that is covered by 2 inches of wet snow. To determine the mass of this snow, use the conversion that 1 inch of wet snow is approximately 0.75 cm of rain. Furthermore, 1 cubic cm of rain has a mass of about 1 gram. What is the total mass of the snow on our 1 square meter of ground (give your answer in kg)?
2. Assume the ambient temperature is exactly freezing (0° C). As the sun shines down on the snow, some of the energy is absorbed to melt the ice into water. You should recall from chemistry that the amount of energy required to melt one kilogram of a substance is called the heat of fusion. The heat of fusion of ice is approximately 334 kJ/kg. Using our answer to question 1, how much heat is required to melt all of the snow?
3. The sun produces tremendous amounts of energy. Each second, approximately 1000 J of energy are delivered to each square meter of the Earth's surface. Assuming all of this energy works to melt the snow, how long will it take to completely melt all of the 2-inch-deep snow cover?
4. Does the answer to question 3 seem reasonable?

In our calculations, we have made quite a few assumptions and also omitted a few important factors.

1. Can you think of any assumptions or omissions we've made that might explain why our calculated value (problem 3) is higher than it should be? Explain!
2. Can you think of any assumptions or omissions we've made that might explain why our calculated value (problem 3) is lower than it should be? Explain!

Post your answers to any of the above questions in the comments section. Please be sure to indicate which question you are addressing.

ACT Test Prep: A Call for Feedback

Photo by Alberto G.

In Physics class, a typical day starts with us taking a look at the "ACT Question of the Day." This takes approximately 5 minutes of class time each day, and  I'm trying to evaluate its effectiveness.

1. Do you think you are learning any "tricks" or test taking strategies by answering these questions every day?
2. Do you think you will be able to perform better on the actual ACT because of our practice on these questions? Why or why not?
3. Do you actually give an honest effort to try to answer the question each day? If not, why? What could we do to encourage you to try harder?

Post your comments here and I'll consider making changes if it makes sense.

Info about Eris

Alexander Novati, Jet Propulsion Laboratory

Recently, astronomers were able to monitor dwarf planet Eris as is transited a star. This means that, from our (Earth's) perspective, Eris traveled directly in front of a distant star. This transit event was informative because it allowed us to measure Eris's size with unprecedented accuracy. The results were a bit of a surprise... ... Eris turns out to be a little smaller than previously thought. This seems to be because Eris's surface is more reflective than previously thought.

Besides astronomers, many people in the general public are interested in the size of Eris. Why does this relatively small object have such an important role to play in our solar system (specifically, the classification of objects within the Solar System)?

If you can't answer the previous question, let's start out with some basic facts about Eris. Where is it? When was it discovered? By whom? How big do astronomers think it is?

Super Cool Video!

Take a minute to watch this amazing video. Isn't this awesome!? Unfortunately, we can't get results like this with normal materials. The physicists involved refer to the disc as a "superconductor." What, exactly, is a superconductor, and why is it necessary for this effect to work?

Keep Sliding

Photo by kimfaires

Imagine giving a hockey puck a nice shove on a huge sheet of ice. We all know that the puck will slide for a long time before coming to rest. However, doesn't Newton's First Law predict that the puck should slide forever? After all, "an object in motion will stay in motion with a constant speed along a straight line path," right?

Why does the stopping puck not violate Newton's First Law? How can Newton's Second Law be used to predict the distance the puck will travel before stopping?

Another Look at Falling Objects

Photo by tiltti.

Greek philosopher Aristotle (384 - 322 B.C.) taught his students heavy objects fall faster than light objects. This idea was believed to be true 2000 years!

1. Who gets credit for first understanding that, in the absence of air resistance, all objects fall (accelerate) toward the ground at the same rate?
2. Consider this thought experiment... ... Imagine dropping a bowling ball and a marble from the same height at the same time. According to Aristotle, the bowling ball will fall faster and land first. According to Aristotle's reasoning, think about what would happen if you tied the two together and dropped them again. Would the combined objects fall faster or slower than the bowling ball alone? Why does this present a paradox? (As an interesting side note, the inventor of this gravity paradox is none other than the answer to question one above!)

Greenland Map Triggers Huge Debate

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A recently published book contains some controversial information about Greenland. Let's work together to examine the issue:

First, some basic facts about Greenland:

1. Greenland is an autonomous country within which larger kingdom?
2. Even though Greenland is part of North America, it is often associated with Europe. Why?
3. Why is it called Greenland? Who gave it this name?

On to the controversial details:

1. What recently-published book was dubbed the "Greatest Book on Earth" by its publishers?
2. What detail(s) about Greenland are significantly different from the last time the book was published?
3. Why has this caused a debate. Be specific!
4. Which side of the debate has the best argument in your opinion?

A Fun Day in Physics!

Courtesy of NASA

It's not often that the news headlines prominently feature a physics story. Today, there are two physics stories reaching headline status! NASA's Upper Atmosphere Research Satellite, or UARS, is projected to crash down to Earth. The exact time and location of the 6-ton satellite is not known, but the chance that it will hit in a populated area is very remote.

1. Has there even been a bigger satellite that has crashed down to Earth uncontrolled? When and what was it? Was anyone or any property hurt?

The other hot topic in physics is the discovery of neutrinos apparently moving faster than light. I read an account of this story at the Wall Street Journal. The article calls neutrinos "an oddball type of subatomic particle."

1. What, exactly, are neutrinos. Where are they produced? Are they rare?
2. Why is this result important? Why does it matter that they travel faster than light?

Do a little reading and share your findings and thoughts about these exciting new stories!

Finding the Line-of-Best-Fit

Students followed directions for MS Excel to find the equation of the line-of-best-fit.

In physics class, students recently collected data from circular objects. Specifically, they measured diameters and circumferences. We wanted to determine the relationship between diameter and circumference for our circles.

To do this, the data was graphed as a scatter plot (C vs. D). Then, Excel was used to calculate the line-of-best-fit (it calls it a linear trendline) and to display the line's equation. In this activity, students were particularly interested in the line's slope because the ratio of C / D should be an experimental way to calculate π.

But, what if a student does not have access to Excel? What are some free tools that will calculate the line-of-best-fit and its slope for a set of data?

1. Search online to some some possible solutions to the above question. Which do you like best?
2. To test these solutions, calculate the slope of the line-of-best-fit for this data:

An Interesting Look at Free Fall

Photo by AleGranholm

A group of Yale physics students used a video camera to analyze the motion of a ball as it fell. The ball was positioned in front of a large measuring scale so its height above the ground could easily be determined. The students reviewed the video of the falling ball frame-by-frame. They used the scale in the background and the video's timecode to study the motion. The following graph shows the expected behavior of a ball in free-fall (neglecting air drag):

This graph show's the actual behavior of the falling ball:

Notice that the second graph is noticeably different from the first one--apparently, the ball did not fall as an object in free-fall! 

Reaction Times

A group of high school students investigated how human reaction time is affected by drinking various soft drinks as part of their year-end physics project. They tested water, Gatorade, and Diet Mountain Dew. Their results are summarized in their report.

They also produced a nice video that documents their procedure.

High Speed Photography

As their year-end project, a group of physics students experimented with high speed photography. They used a PASCO photogate to connected to a strobe light. The strobe was the only source of light in the room, so the students were able to automatically capture the photo at just the right time. The photos below show a table tennis ball and a bottle cap splashing down into a beaker of water.

The Ballista

As their year-end physics project, a group of students designed, built, and tested a ballista. They also recorded various attributes of the arrow's trajectory. For complete details, watch the summary video:

Medieval Trebuchet

The completed trebuchet is prepared for launch.

A sample of the group's calculations.

As part of a year-end project, a group of high school physics students created a working trebuchet. The trebuchet was a cross-curricular project, counting for both physics and history classes. For physics, the students working out the theoretical range, trajectory, and speed, and compared to the actual results. Watch the group's video for an overview.

This video show's the trebuchet in action at the first inaugural renaissance festival:

Lights, Camera, Green Screen?

Comedy Central's popular tosh.0

Anyone who has ever watched TV has more than likely seen these technological wonders known as a green screen. Only thing is, they probably don't know it. The purpose of a green screen is to change a background or wall into something it's really not. Video producers, news producers, and even TV shows such as Tosh.0 make use of the technology, bringing us their information in viewer friendly formats. But how do they do it?

In order for the screen to work, it needs to be kept under a specific set of conditions. What are these conditions? What needs to be done in order to produce those flawless images we see every day on TV? How does the screen work, what is it that allows us to see the images and videos in the background? Research green screens and try to answer these questions.

3G or 4G?

Photo by Arafath Hashmi

Nowadays smartphones are becoming more and more widespread. Almost always when you go to purchase a phone and sign a contract you need to pay extra to use the internet, there are various types of internet bundles you can choose from. This is when it becomes cloudy for many people. Phone companies do a terrific job of making their products seem as if they are the best, boasting of extremely fast internet or inexpensive deals.

There is 3G internet and a new 4G. The introduction of 4G internet has brought along numerous questions. For example, what is it, what's the difference between the two, and is it really all that better? Research 4G and try to answer some of these questions.

Circuit Software

Photo by deejayres

We've been analyzing some basic series and parallel circuits in class. After doing many calculations, many students realize that this kind of work can be repetitive and tedious. Many of the processes we do in our analysis can be easily performed on a computer. For example, we often combine many resisters into a single,  "equivalent" resistance, and then use Ohm's Law to determine the current that will flow through each component of the circuit.

Consider this (easy) problem concerning circuit analysis... ... A 12-V battery is connected to a 100-ohm and a 200-ohm resistor arranged in parallel. This parallel arrangement is then connected in series to a third resistor that has a resistance of 50 ohms and then back to the battery. What current will flow through the 100-ohm resistor? Surely a computer can solve this problem automatically, right?

Do some searching online and see if you can find a program or, better yet, a web applet that allows the user to add electrical components to a blank canvas and then simulates the results. Post a link to your favorite analysis software, and post the answer to the above question.

Gun Control: Momentum

Photo by Phillip C.

There has always been the rumor of bullets falling from the sky. That is, another person shooting a bullet in the air at a high angle (say, 45 degrees) and the bullet coming down miles away and landing on some poor, unsuspecting soul. The major point of this discussion, though, is would that bullet kill someone? We can find this using the theory of momentum and a little bit of research. The impact time of the bullet would be roughly.0014 seconds, and do some research on the forces it would take to kill a person, preferably by hitting their skull.

Take this situation: There is a young boy gun hunting on earth. He is hunting with a 9mm handgun. He decides to be irresponsible, lifts his gun 3 meters off of the ground, and fires two shots: one straight in the air, and one at a 45 degree angle. The bullet's massis 7.45 grams and it has an initial velocity of 366 m/s. The terminal velocity, or the maximum speed a bullet can travel, is about 166 ft/s. Assuming that the acceleration of gravity is 9.8 m/s^2, would any of these bullets have the force necessary to kill a human? Calculate please, don't assume.

Harmony: It's all physics!

Picture by KMLA Orchestra

Music is beautiful, emotional, and enjoyable. It also becomes extremely complex. Even looking at the basics of things such as music theory, the average viewer can become as lost as a first grader trying to learn Advanced Calculus. But let's try and simplify music a little bit first.

To say it bluntly, music is simply variations of pitch and volume. Where it gets complex is when you start adding things such as harmony. Simplified, harmony is when two or more notes are played and they simply sound nice together. Harmony is used in many forms of music, so chances are you know what it sounds like. But what creates this sound when looking at it from a physics perspective?

In physics you learn(ed) that different notes have a related frequency. From a physics point of view, what correlations do two harmonizing notes have with each other when viewing their frequencies? Are there any specific formulas or ratios that make a tear-jerking or powerful chord? Do some research on harmony and share any ratios, formulas, or facts on harmony. ALSO, see if you can find a visual representation of harmony at work, preferably a graph of the waves.

On a Higher Note...

We have all seen it in the movies: a woman belts out a loud, high pitch note that can shatters the glass in the entire building, from the wine glasses to the windows.  But can a voice really reach a frequency high enough to shatter glass?  Glass has a natural resonant frequency which is the speed at which it will vibrate if disturbed by a stimulus such as a sound wave.  However, not all glass has the same natural resonance.  Wine glasses are especially resonant because of the goblet shape which is why, when struck, they emit a pleasant, ringing sound.  It is at that ringing note a singer must reach in order to shatter the glass, vibrating the air molecules around the glass, causing the glass to vibrate as well.  If the corresponding note is sung loud enough, the glass will eventually vibrate its self into smithereens.  But what is that frequency a singer sings to vibrate a wine glass and just how loud would she have to sing to make it shatter?  Also, what else would contribute to making the glass easier to break?  Research the idea and tell me your findings and thoughts.

Helicopters: A Spin on Physics

picture: KNOWN MALTA by Peter Grima

The first early record of a design similar to the helicopter was that of Da Vinci during the Renaissance period. A original concept of having a structure lift off the ground and hover in mid air with personnel on board. Many had thought the idea absurd and impossible, however in 1904 the first helicopter flew and a better more successful version the German Focke-Wulf Fw 61 flew in 1924. The helicopter is very complex and has much improved over the decades. Modern choppers, as many call them, such as the AH64-A Apache, the AH-1 Cobra, and the MI-24 Hind have been suited with top of the line technology and loaded with weapons for military use. Even though many are shaped different and are of different sizes they all run under the same basis for flight. They each have a rotor atop of the platform that rotates to thrusting the air above it downwards to produce a counteractive push upwards on the chopper. What is it about a helicopter that keeps it stable? Wouldn't common sense tell you that this piece of rotating metal would loose control and send it's occupants to theirs deaths? Do some research and see why the helicopter is able to fly the way it does? What are some interesting facts about them? How can they be useful and name some of the ways they have been used and where. I look forward to your comments

Waves: Refraction, Diffraction, and Interference

Refraction of light through glass. Photo by Joost J. Bakker.

Refraction is the bending of a wave as it its speed changes (usually as a result of going from one medium to another). Light provides an excellent example of refraction as it passes from glass to air or from water to air. However, other types of waves can refract as well. Consider a sound wave... ... Can sound refract? Do a little poking around on the internet. Can you find any descriptions of physical phenomena that can be explained by sound refraction?

Diffraction is the bending of light as it passes near an edge. In class we saw how a human hair can diffract a beam of laser light to form an interesting pattern. Look up the term "diffraction grating." What is it and what it is used for?

Interference occurs when two or more waves occupy the same space at the same time. There are many animations and simulations available online to help to visualize wave interference. My favorite is the virtual wave table on the phet site. Search around and post a link to a site you find useful.

Radiation in Japan

Fukushima Nuclear Power Plant Explosion, March 14th

March 11, 2011

A earthquake of a magnitude of 9.0 on the Richter scale hit Japan near the coast of Honshu.  The earthquake then triggered massive tsunami waves reaching up to 23.6 m in height minutes after the quake had hit.  The waves reached nearly 10 kilometers inland.  Millions were left without electricity and water, which inadvertently led to three nuclear reactors exploding due to hydrogen build up when the cooling system failed.  On March 18, the head of the International Atomic Energy Agency, Yukiya Amano, declared the crisis extremely serious, which lead to anyone within 20 kilometers of the Fukushima I Nuclear Power Plant and 10 kilometers within the Fukushima II Nuclear Power Plant had to evacuate the area immediately.  But just how deadly is the nuclear material in the reactors.  What exactly is in the reactors that is causing this chaos?  Just how long does it take the radoactive material to travel, how far would it be able to travel, and how deadly would it still be?  Share your thoughts and opinions.

Da Vinci in the Renaissance

Image by MAMJODH on Flickr

     Leonardo Da Vinci, a well renown scientist, is known for his artwork, inventions, and craftiness. Everyone today would agree that he was a man ahead of his time. He developed things like the portable bridge, armored cars, and flying machines. He also worked with cannons and catapults and was a scientist wanted by every country for his wide knowledge and ability to think outside the box. Many of his inventions and concepts came about during the Renaissance--a turning point for man in history. Da Vinci even developed the early version and whole idea of the battle tank. It was designed to be run by many men and be mobile along the battlefield (a moving fortress). However within the designs there was a huge error where two gears opposed each other. This sort of error would have made the tank incapable moving or defending itself. Experts believe that Da Vinci being the mastermind that he was was too intelligent and observant to overlook such a major flaw in the design and the flaw was actually purposely placed there in order to protect it from being stolen and used by other countries and scientists we desperately wanted his insight and inventions. What are some other inventions and ideas of inventions of Da Vinci that are interesting? Is there a underlying fact that you find intriguing? How are some of his inventions influential in our world today? I  am looking forward to your responses

Power: An Introduction to Google Spreadsheets

Students justed completed a very quick lab where they calculated how much power their lower body produces as they jump into the air. The results from each group were entered into a Google spreadsheet.

1. It will be easiest to follow these instructions if you keep this page open all the time and use separate tabs for the activities.
2. To create a Google spreadsheet, you will need a Google account (it's free). If you don't already have one, go to the Google sign-in page and follow the instructions.
3. Make sure you've signed in to your Google account.
4. Click on the screen shot of the spreadsheet, and the link will open the spreadsheet we generated in class. You will able to view the spreadsheet, but not edit it (I've set it up that way on purpose).
5. Copy the data from our class spreadsheet to your computer's clipboard.
6. Click the "Documents" link near the top of the spreadsheet.
7. Find the drop-down list titled "Create new" near the left side of the screen. Click on it and select "Spreadsheet."
8. Paste the copied data into this new spreadsheet. Since this is your spreadsheet, you are able to edit it and add to it.
9. Congratulations, you have created your first Google spreadsheet!

Let's use the spreadsheet to analyze the data a little further. 

1. In column C, insert a formula that will express each student's power in horsepower (remember, 1 hp = 746 watts). For example, you can do this for cell c2 with the formula "=b2/746".
2. Have the spreadsheet calculate and display the average values for each column at the bottom of the data.
3. I'd like to investigate the relationship between the measured time (column A) and the power (column B). Let's do this by creating a scatter plot of that data. To do this, highlight just that data, click on the "Insert chart" icon, and select the appropriate type of chart.
4. When you're finished, click on the "Share" button in the upper-right portion of the screen to allow anyone online to see your completed work. (They will be able to view it, but not edit it.) Copy the automatically-generated link to your spreadsheet, and post it in the comment section to this post.

Smart car: Safe haven or death trap

Photo by nikiretro

The new smart car that has just recently been released has been flooding the market. With its five star crash safety rating and its highly efficient gas mileage there is no question to why it is such a attraction. Mercedes-Benz the owner of the smart car claims that they have conducted rigorous testing and believe the small compact car to be safe as any other car on the road. Many people however has scrutinized the idea of such a small car. They don't perceive the words small and safe can be placed in the same sentence. The smart car has a length of about 100 inches and weighing in at 730 kg  it comes to no surprise why some are concerned. Does physics support the claims of the scientists to the capability of the smart car? Do some research to find out the explanations of both sides of the argument. What do you think about the controversy? How does momentum play a role in the physics of keeping a driver safe? I'm looking forward to your responses.

A Physics to English Dictionary?

Photo by Horia Valran

Physics students will begin studying the concept of momentum this week in class. As I was collecting my thoughts about how I plan to introduce momentum, it occurred to me that we use the word momentum in regular (English) language. In physics, momentum is defined quantitatively as the product of mass and velocity. Dictionary.com defines momentum (in common language, at least) as "impetus, as of a physical objector course of events." These two definitions--the physics one and the English one--complement each other nicely. Just as in common usage, an object in physics with a lot of momentum will be difficult to stop!

Can you think of other physics words or terms that also appear in the common vernacular? Do these words have similar meanings, or are they considerably different? Please give specific examples in your comments.

A Second Sun for Earth?

An artist's idea of what this event could loook like from Earth

The star Betelgeuse has been making the news lately. Betelgeuse is a supergiant star with a mass more than 100,000 times that of the Sun and one of the brightest known starts in our galaxy. Because of its huge size, it is burning through its fuel at an incredible rate.

Betelgeuse is near the end of it's life for sure, and that end could come at any time. In fact, Betelgeuse is due to go supernova at any (astronomical) time. It's important to note that we're talking about astronomical time where 1,000 years is considered just the blink of an eye.

How would a Betelgeuse supernova affect the Earth? Do a little research online, and post your comments?

1. Where is Betelgeuse located in our sky?
2. What is a supernova?
3. Would it be visible from Earth?
4. Would it be harmful?
5. Why are some news stories calling it a potential "second sun?"

Daedalus' Flight

Daedalus and Icarus by van Dyck

Ever thought of what it would be like to fly in the sky, soaring high with the birds?  Ever imagined what it would feel like to have wings?  How about to fly high above the sea to escape with your life?  This is what Daedalus and his son, Icarus, hoped to accomplish in the dead of night to escape from the deadly wrath of the Minotaur, a mythological of beast from Greek that was half-bull, half-man, in the Labyrinth with wings constructed from feathers and wax.  In the story, Daedalus sketched out a wing design for the feathers to be applied to.  Then, using that design, build a wooden lattice in the shape of an outstretched wing and covered it from feathers that he had gathered, making them stick to the framework with heated wax.  He attached the wings to his and Icarus’ arms, and then took off over the sea.  However, despite his father’s warning, Icarus flew too close to the sun, where the heat then melted the wax keeping the feathers to the frame, and he plunged into the sea and drowned.  But is a flight such as this possible?  Can we as humans really fly as the birds in the sky do, flapping our own set of wings and soaring on air currents?  What needed physics would behind this to make it possible?

Tell me your thoughts and ideas.  Be sure to give detail on why.

Physics of Pole Vaulting: Part 1

Pole vaulting, one of the most exhilarating and technologically complicated events in track and field, is only pursued by the most daring of individuals. In pole vaulting a vaulter's goal is to clear, or get over, a horizontal bar at set hight. In a typical competition, a vaulter may make seven or eight jumps. During a jump, a vaulter is trying to convert his energy from his horizontal velocity and transfer it into vertical energy. There are many factors that effect the outcome of a vault. This makes it difficult to look at the cause of a mistake or error, for all the factors are interrelated to each other. By neglecting certain factors it makes it easier to see the physics behind the pole vaulting.

Suppose a vaulter sprints toward the pit at 7 m/s. When the vaulter reaches the pit, his pole launches him at an angle of 83 degrees with the horizontal toward the horizontal bar. In what time will the vaulter reach his peak? What height will this be? (Think of the vaulter as a projectile)

Consider your answer. What factors do you think would affect the height of a vaulter? (There are many!)

MythBusters' Math Mistake?

Screenshot from 11/12/2011

I caught the last 5 minutes of MythBusters last night (episode "No Pain No Gain"). They were testing to see how "cursing" affects the amount of time people can tolerate having their arms in a tub of ice water--the myth being that cursing will increase one's pain tolerance.

Look at the screenshot of the MythBusters' results. Grant was able to keep his arm in the ice water for 38 seconds without cursing and for 118 seconds while cursing. The column labeled "% Change" strikes me as very odd.

1. By using the MythBusters' data, try to determine the formula or process they are using to calculate "% Change."
2. How should percent change be computed? What data should appear in that column?
3. Did the MythBusters make a mistake? If so, make a post on the forum for that episode and leave a link here to share with us.

The Physics of Iron Man: Flight

Being the extreme science fiction fan that I am, I have always favored Iron Man as my favorite superhero. Not only does he fight crime, but he fights crime... with science. Or so I thought. A few years ago I found myself in the seat of a movie theater, revving up my action engines and preparing for the onslaught of awesomeness the Iron Man movie planned to deliver. With this superhero brought to the silver screen, however, I found myself mumbling under my breath about how just about everything he was doing was physically impossible. Or was it? By making a few assumptions about his fictional technology, I decided it was time to make a few calculations. Thus, this short series was born.

Over the next few weeks, I will be occasionally be posting a physics question regarding Iron Man's comic book and "big screen" technology. This, of course, is the first post.

Today's question is about Tony Stark's (Iron Man's actual name) flight. This is truly a spectacle to behold, and one of the original purposes for the creation of the suit, according to the film. In fact, it was this very feature that allowed Tony to escape the terrorists in the film! But let's take a closer look at that scene...

During the scene, Tony builds a gigantic robot that needs the help of mechanical power in order to actually allow it to move easily. In other words, it weighed a lot. So, with the assumption that his main resources was stainless steal (The terrorists were supplying him, remember!), the suit probably had a mass of about 2,360 kilograms. This includes the many dense plates of armor that he was wearing, along with the weapons, and the fuel reserves. Tony, being an average human adult male probably weighed about 75 kilograms.

Photo by Daniel Spiess.

Later in the scene, Tony walks outside of the cave he was trapped inside, and, in a way to escape the terrorists, uses his first rocket boots about 20 meters from the mouth of the cave to propel himself into the air. Unfortunately, Tony is only able to sustain his flight for roughly 7 or so seconds.

This brings us to question #1: How much force was actually needed to lift the first Iron Man (Tony in the prototype suit) off the ground? This is assuming that the acceleration of gravity in the Middle East is 9.8 m/s^2.

Now for question #2: Assuming that he is able to obtain enough force to instantly accelerate him to a flight speed of 90 m/s, and he sustains this speed for the length of his flight, how high will Tony get before he runs out of fuel if he launched himself at a 35 degree angle?

Question #3: At the top of his flight, Tony runs out of fuel. From here he falls down onto the ground in a crash. Assume that Tony leveled himself out the moment he ran out of fuel. How far from the mouth of the cave is he at this point, assuming he traveled in one direction?

Question #4: How fast will Tony be falling just before he hits the ground?

Now, lets look at how much force his rocket boots are creating.

Question #5: How much force would be needed for Tony to lift off of the ground WITHOUT the suit?

Final Question, #6: How many times more is needed for a suited Tony to lift off as compared to an unsuited Tony?

Discuss your findings. It's kind of ridiculous.

Coming Soon: Guest Authors

We are pleased to announce that there will soon be three new authors joining the Yale High School Physics Blog. These authors are students at Yale High School currently taking Independent Study Honors Physics II. They will be writing posts about  physics topics that enrich content covered in the physics classroom, physics as it appears in popular culture, and how physics topics impact people in their daily lives. The authors are eager to read feedback about their posts.

Please be sure to check back often as these posts are published. Let's get a dialog going!

Physics from a Historical Perspective

Photo by Thorne Enterprises

Charles Day from Physics Today writes a very interesting column comparing how students learn US government to how they learn physics. Please read Day's excellent article before posting a comment here.

The US Constitution is the foundation upon which our entire government is built. Even though it was written in 1787, the Constitution is not only relevant but fundamental to any study of US government. Students of US government often are asked to directly read and study this document.

In physics, many (if not most) topics of study have changed radically since 1787. Physics teachers rarely ask their students to read or study physics books or papers from that far in the past.

1. Day talks about several topics of modern physics that were not even known when the Constitution was written. What specific topics does he mention?
2. One of the texts mentioned in Day's article is Newton's famous work usually called simply Principia. What is the full title of this work? When was it written? What is it about, and why is it so important?
3. Do you think physics students would gain a deeper understanding of physics if they studied historical texts like Principia? Why or why not?

A Call for Myths!

Physics students will soon be working on a "MythBusters" project modeled after the show MythBusters. Mythbusters is a science show that airs on the Discovery Channel on Wednesdays from 9 – 10 PM (and re-runs can be found on the Discovery Channel throughout the week). Each hour-long episode features 3 – 4 science myths or questions that are put to the test. The show’s hosts introduce the myth, design an experiment, perform the experiment, and then analyze the data to label the myth as “busted,” “plausible,” or “confirmed.”

In our project, students will carry out an experiment to test their own myths. Perhaps the hardest part of this assignment is coming up with a good myth to test. Myths can range for commonly-repeated statements such as "you can't fold a piece of paper in half more than 7 times" to cartoon physics such as "banana peels are really slippery" manufactures' claims about their products.

For those interested, details about the project can be found in the handout.

In the comments section, I'd like to know what myths you've heard about and would like to suggest to be tested. If possible, I'd like to avoid having any groups test a myth that has been featured on MythBusters. Post away!

Equilibrium Software

Photo by Felipe Gabaldon

Calculating individual forces within systems in equilibrium can be a daunting task! As we've seen in class, the process involves drawing a free-body diagram, resolving forces into components, and writing equations for each dimension. Almost always, this process leads to solving a system of equations. Depending on the particular problem, this system of equations can be quite difficult.

Computers are well-suited to doing tedious calculations. They certainly have the ability to solve the system of equations mentioned above. Do a little searching online.

1. What are some software programs/packages that engineers use to solve problems of static equilibrium?
2. Are there any freeware programs that can solve statics problems?
3. Can you find any applets online that allow a user to manipulate beams, cables, masses, etc., and will then display the resulting force in a particular piece of the structure?

Share your links in the comments.