Virtual lab: Series and Parallel circuits
Learn about electrical circuits with the PhET Circuit construction kit
* Briefly play with the app, learning the drag-and-drop components
* Follow the instructions. Carefully write answers in your notebook.
* Accurately answer questions in complete sentences, at a high school level.
This must be completed in class to get credit. Unless you have an excused absence, you can’t make up the lab.
Learning Goals:
Develop a general rule regarding how resistance affects current flow,
when the voltage is constant.
Learn how changing resistance values affect current flow in both series and parallel circuits.
Series Circuit A

Right click on the resistor, change the value of the resistor and observe what happens to the rate that the electrons move through it. The rate at which the electrons move is called current. Current is measure in Amps
(A) Make a general rule about the relationship between current and resistance.
– 10 points for circuit and accurate answer.
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Parallel Circuit B

Make observations & draw conclusions. – By right clicking on the resistors, change the values of the resistors, making one very high and one very low and visa versa.
Look for what happens to the current flow through the different resistors.
With regards to circuit B:
(a) Describe current at different locations in the circuit, esp. rate of the current and the value of the resistors.
(b) Explain your observations of the current flow in terms of the water tank model of electricity given to you in class
(c) Describe how your general rule from step 2 relates to your observations
– 20 points for circuit and accurate answer.
______________________________
Circuit C

Change the values of the resistors, making one very high and one very low, and visa versa.
(a) Look for what happens to the current flow through the different resistors.
(b) Describe current at different locations in the circuit.
(c) Explain observations of the current flow in terms of the water-flow analogy.
(d) Describe how your general rule from the beginning relates to your observations.
Water flow analogies for electrical current
– 20 points for circuit and accurate answer.
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Circuit D: voltage in a series circuit
Build the series circuit shown below. On the left-hand menu, click voltmeter. You can drag-and-drop the red and black leads.
In your notebook, add the following definitions:
A lead is an electrical connection that comes from some device. Some are used to transfer power; ours are used to probe circuits.
A multimeter is a measuring instrument that combines multiple meters (measuring devices) into one Typical multimeters include
ammeter = measures I (current)
metric unit of current is amperes (A)
ohmmeter = measures r (resistance)
metric unit of resistance is ohms (Ω)
Ω is the Greek letter omega.
voltmeter = measures v (voltage) in a battery,
or the voltage drop across a part of a circuit.
metric unit of voltage is the volt (v).

With the knife-switch closed, what is the voltage drop across:
- the battery
- the light bulb
- the knife-switch
- the resistor
With the knife-switch open, what is the voltage drop across:
- the battery
- the light bulb
- the knife-switch
- the resistor
____________________________
Circuit E: voltage in a parallel circuit
Build the series circuit shown below. On the left-hand menu, click voltmeter.
You can drag-and-drop the red and black leads.
What is the voltage drop across:
- the 2 batteries
- the resistor in the middle
- the light-bulb
- Points A and B on the wires.

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Circuit F: Measuring both I and V
Build the circuit shown here. Use the voltmeter to measure voltage, and the ammeter to measure current. Carefully fill in the 2 data tables. After you have taken the data, answer
(a) Compare the voltage numbers before you changed the resistance, to after you changed the resistance.
(b) Look just at the left column (default values) for current. Compare your numbers, to their locations on the circuit: What’s the relationship between the amount of current in one part of the circuit, to another? (Thinking of the water-flow analogy may be helpful.)
(c) Look at the right column for current. How did changing the value of one resistor affect the circuit (if at all?)




Learning Standards
Massachusetts 2016 Science and Technology/Engineering (STE) Standards
HS-PS2-9(MA). Evaluate simple series and parallel circuits to predict changes to voltage, current, or resistance when simple changes are made to a circuit.
Technology/Engineering Progression Grades 9-10
The use of electrical circuits and electricity is critical to most technological systems in society. Electrical systems can be AC or DC, rely on a variety of key components, and are designed for specific voltage, current, and/or power.
Emergent phenomenon
Thomas T. Thomas writes:
From our perspective at the human scale, a tabletop is a flat plane.

but at the atomic level, the flat surface disappears into a lumpy swarm of molecules.
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Aficionados of fractal imagery will understand this perfectly: any natural feature like the slope of a hill or shore of a coast can be broken down into smaller and smaller curves and angles, endlessly subject to refinement. In fractal geometry, which is driven by simple equations, the large curves mirror the small curves ad infinitum.
The emergent property is not an illusion… The flatness of the tabletop is just as real—and more useful for setting out silverware and plates—than the churning atoms that actually compose it. The hill and its slope are just as real—and more useful for climbing—than the myriad tiny angles and curves, the surfaces of the grains of sand and bits of rock, that underlie the slope.
Emergent property works on greater scales, too. From space the Earth presents as a nearly perfect sphere, a blue-white marble decorated with flashes of green and brown, but still quite smooth. That spherical shape only becomes apparent from a great distance. Viewed from the surface, it’s easy enough for the eye to see a flat plane bounded by the horizon and to focus on hills and valleys as objects of great stature which, from a distance of millions of miles, do not even register as wrinkles.
Emergent properties come into play only when the action of thousands, millions, or billions of separate and distinct elements are perceived and treated as a single entity. “Forest” is an emergent property of thousands of individual trees. The concept of emergent properties can be extremely useful to describe some of the situations and events that we wrestle with daily.
The Human Condition: Emergent Properties, Thomas T. Thomas, 8/11/2013
also
NOVA ScienceNow Emergence, PBS
Examples
Conway’s game of life
https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life
http://emergentuniverse.wikia.com/wiki/Conway%27s_Game_of_Life
http://www.scholarpedia.org/article/Game_of_Life
http://www.conwaylife.com/
BOIDS: Birds flocking
Boids Background and Update by Craig Reynolds
http://www.red3d.com/cwr/behave.html
http://www.emergentmind.com/boids
Coding: 3 Simple Rules of Flocking Behaviors: Alignment, Cohesion, and Separation
https://en.wikipedia.org/wiki/Flocking_(behavior)
Classical physics
Classical physics is an emergent property of quantum mechanics
TBA
External links
Online Interactive Science Museum about Emergence
How Complex Wholes Emerge From Simple Parts Quanta magazine
Learning Standards
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
Appendix VIII Value of Crosscutting Concepts and Nature of Science in Curricula
In grades 9–12, students can observe patterns in systems at different scales and cite patterns as empirical evidence for causality in supporting their explanations of phenomena. They recognize that classifications or explanations used at one scale may not be useful or need revision using a different scale, thus requiring improved investigations and experiments. They use mathematical representations to identify certain patterns and analyze patterns of performance in order to re-engineer and improve a designed system.
Next Gen Science Standards HS-PS2 Motion and Stability
Crosscutting Concepts: Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena. (HS-PS2-4)
A Framework for K-12 Science Education
Scale, proportion, and quantity. In considering phenomena, it is critical to recognize what is relevant at different measures of size, time, and energy and to recognize how changes in scale, proportion, or quantity affect a system’s structure or performance…. The understanding of relative magnitude is only a starting point. As noted in Benchmarks for Science Literacy, “The large idea is that the way in which things work may change with scale. Different aspects of nature change at different rates with changes in scale, and so the relationships among them change, too.” Appropriate understanding of scale relationships is critical as well to engineering—no structure could be conceived, much less constructed, without the engineer’s precise sense of scale.
Dimension 2, Crosscutting Concepts, A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (2012)
http://necsi.edu/guide/concepts/emergence.html
Quantum teleportation
Big step for quantum teleportation won’t bring us any closer to Star Trek. Here’s why
By Adrian Cho, Sep. 19, 2016 , Science (AAAS)
Two teams have set new distance records for quantum teleportation: using the weirdness of quantum mechanics to instantly transfer the condition or “state” of one quantum particle to another one in a different location. One group used the trick to send the state of a quantum particle of light, or photon, 6.2 kilometers across Calgary, Canada, using an optical fiber, while the other teleported the states of photons over 14.7 kilometers across Shanghai, China.
Both advances, reported today in Nature Photonics, could eventually lead to an unhackable quantum internet. But what else is quantum teleportation good for? And will we ever be able to use it to zip painlessly to work on a frigid January morning?
When will this stuff enable us to travel by teleportation?
Sorry to disappoint, but the answer is never. In spite of its name, quantum teleportation has nothing to do with the type of teleportation depicted in the television show Star Trek and other science fiction stories. Such teleportation generally involves disintegrating a material object, somehow beaming the contents through space, and instantly and perfectly reassembling the object in some distant location. In quantum teleportation, nothing is disintegrated and reassembled and no matter travels anywhere. What’s more, the process works only at the level of individual quantum particles: photons, electrons, atoms, etc. Long and short, quantum teleportation and “real” teleportation have nothing in common but the name.
But if quantum teleportation doesn’t move things, then what does it do?
Compared with sending an away team to a planet’s surface, quantum teleportation aims to do something both much less ambitious and much more subtle. Quantum teleportation instantly transfers the condition or “state” of one quantum particle to another distant one without sending the particle itself. It’s a bit like transferring the reading on one clock to a distant one.
What’s so impressive about reading one clock and setting a second the same way?
The quantum state of a particle like a photon is more complex and far more delicate than the reading of a clock. Whereas you can simply read the clock and then set the other clock to the same time, you generally cannot measure the state of a quantum particle without changing it. And you cannot simply “clone” the state of one quantum particle onto another. The rules of quantum mechanics don’t allow it. Instead, what you need to do is find a way to transfer the state of one quantum particle to another without ever actually measuring that state. To continue with the clock analogy, it’s as if you’re transferring the setting of one clock to another without ever looking at the first clock.
How could that possibly work?
It’s a bit complicated. To get a feel for it you need to know something about quantum states. Consider a single photon. A photon is a fundamental bit of an electromagnetic wave, so it can be “polarized” so that its electric field points vertically or horizontally. Thanks to the weirdness of quantum mechanics, the photon can also be in both states at once—so the photon can literally be polarized both vertically and horizontally at the same time. The amounts of vertical and horizontal help define the state of the photon.
But it gets even more complicated than that. In addition to the mixture of vertical and horizontal, the photon’s state is defined by a second parameter, which is a kind of angle called the “phase.” So the actual state of the photon consists of both the mixture of vertical and horizontal and the phase. It can be visualized with the help of an abstract sphere or globe, on which the north pole stands for the pure vertical state and the south pole stand for the horizontal late state.
The precise state of the photon is then a point on the globe, with the latitude giving the balance of vertical and horizontal in the state and the longitude giving the phase. Thus, for example, every point on the equator stands for a state in which the photon is in an equal mixture of vertical and horizontal, but in which the phase, which can be probed in certain more complicated measurements, is different.
So why can’t you just read the point off the globe?
You can’t because measurements of quantum particles provide only limited information. Given a photon in some unknown state, you cannot ask what the “coordinates” of the state on the globe are. Instead, you must perform an either/or measurement. The most simple would be: Is the photon polarized vertically or horizontally? That measurement will give one result or the other with probabilities that depend on the exact mixture of vertical and horizontal in the state. But it won’t tell you the phase. And it will “collapse” the original state, so that the photon is left pointing at one pole or the other, in a state that is either purely vertical or horizontal. That disturbance of the original state is unavoidable in quantum theory.
A photon’s state is described by a point on a “Bloch sphere.” The point’s latitude (angle θ) determines the mixture of horizontal and vertical polarization. The longitude (angle φ) has no classical analog but leads to many weird quantum effects.
A photon’s state is described by a point on a “Bloch sphere.” The point’s latitude (angle θ) determines the mixture of horizontal and vertical polarization. The longitude (angle φ) has no classical analog but leads to many weird quantum effects.

But if you can’t measure the exact state of the photon, how do you transfer it?
You need more photons and another weird bit of quantum mechanics. Two photons can be linked through a subtle connection called “entanglement.” When two photons are entangled, the state of each photon is completely uncertain but the two states are correlated. So, on our abstract globe, the position of each photon remains completely undetermined—it is literally pointing in every direction at once. But, in spite of that uncertainty, the states of the two photons can be correlated so that they are guaranteed to be, say, identical. That is, if you did a fancy measurement that collapsed one photon in the direction on our globe of 40º north, 80º west, you would know the second one would instantly collapse into the same state, no matter how far away it is. Such pairs are crucial to quantum teleportation.
Here’s how it works. Suppose you have two people, Alice and Bob, with a third, Charlie, in the middle. Alice prepares a photon that she wants to teleport—that is, she sets its position on the abstract globe. She sends it down an optical fiber to Charlie. At the same time, Charlie prepares a pair of entangled photons. He keeps one and sends the second one on to Bob.
Now, here’s the tricky part. When Charlie receives Alice’s photon he can take it and the one he’s kept and do a particular type of “joint” measurement on them both. Because quantum measurements collapse the states of photons, Charlie’s measurement actually forces those two photons into an entangled state. (Charlie’s measurement actually asks the either/or question: Are the photons in one particular entangled state or a complementary one?)
But as soon as Charlie does the entangling measurement on the two photons he has—the one he got from Alice and the one he kept from the original entangled pair—a striking thing happens. The photon he sent to Bob instantly collapses into the state of Alice’s original photon. That is, the globe setting of Alice’s photon has been teleported to Bob’s even if Bob is kilometers away from Charlie—as he was in these two experiments.
But why does that happen?
The experiment depends crucially on the correlations inherent in entanglement. Beyond that, to see why the state of Alice’s photon ends up transferred to Bob’s, you pretty much have to go back and work through the math. Once you get used to the notation, anybody who has taken high school algebra can do the calculation. That is one of the things algebra is good for.
Is this what the physicists actually did?
Close. The only difference is that they used two slightly different arrival times for the basic states of the photons, not different polarizations. The hard part in the experiments was guaranteeing that the two photons sent to Bob arrived at the same general time and were identical in color and polarization. If they were distinguishable, then the experiment wouldn’t work. Those were the technical challenges to teleportation over such long distances.
So what is this possibly good for?
Even though it’s abstract, quantum teleportation could be used to make a quantum internet. This would be like today’s internet, but would enable users to transfer quantum states and the information they contain instead of classical information, which is essentially strings of 0s and 1s.
Currently, physicists and engineers have built partially quantum networks in which secure messages can be sent over optical fibers. Those technologies work by using single photons to distribute the numerical keys for locking and unlocking coded messages. They take advantage of the fact that an eavesdropper could not measure those photons without disturbing them and revealing his presence. But right now, those networks aren’t fully quantum mechanical in that the message needs to be decoded and encoded at every node in the network, making the nodes susceptible to hacking.
With quantum teleportation, physicists and engineers might be able to establish an entanglement connection between distant nodes on a network. In principle, this would enable users at those nodes to pass encoded messages that could not be decoded at intermediary nodes and would be essentially unhackable. And if physicists ever succeed in building a general-purpose quantum computer—which would use “qubits” that can be set to 0, 1, or both 0 and 1 to do certain calculations that overwhelm a conventional computer—then such a quantum network might enable users to load in the computer’s initial settings from remote terminals.
When is that going to happen?
Who knows? But a quantum internet seems likely to show up a lot earlier than a general-purpose quantum computer.
Huh. Cool! But no beaming to work during the winter?
Sorry, you’ll still have to bundle up and face the cold.
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Possible habitat for life on Enceladus, a moon of Saturn

– This graphic illustrates how Cassini scientists think water interacts with rock at the bottom of the ocean of Saturn’s icy moon Enceladus, producing hydrogen gas. Credit: NASA/JPL-Caltech
____________________________________
Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other “ocean worlds” in our solar system and beyond. The findings are presented in papers published Thursday by researchers with NASA’s Cassini mission to Saturn and Hubble Space Telescope.
In the papers, Cassini scientists announce that a form of chemical energy that life can feed on appears to exist on Saturn’s moon Enceladus, and Hubble researchers report additional evidence of plumes erupting from Jupiter’s moon Europa.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. ”These results demonstrate the interconnected nature of NASA’s science missions that are getting us closer to answering whether we are indeed alone or not.”
The paper from researchers with the Cassini mission, published in the journal Science, indicates hydrogen gas, which could potentially provide a chemical energy source for life, is pouring into the subsurface ocean of Enceladus from hydrothermal activity on the seafloor.
The presence of ample hydrogen in the moon’s ocean means that microbes – if any exist there – could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. This chemical reaction, known as “methanogenesis” because it produces methane as a byproduct, is at the root of the tree of life on Earth, and could even have been critical to the origin of life on our planet.
Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur.
With this finding, Cassini has shown that Enceladus – a small, icy moon a billion miles farther from the sun than Earth – has nearly all of these ingredients for habitability. Cassini has not yet shown phosphorus and sulfur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements.
“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.
The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its last, and deepest, dive through the plume on Oct. 28, 2015. Cassini also sampled the plume’s composition during flybys earlier in the mission. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water, about 1 percent is hydrogen and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia.
The measurement was made using Cassini’s Ion and Neutral Mass Spectrometer (INMS) instrument, which sniffs gases to determine their composition. INMS was designed to sample the upper atmosphere of Saturn’s moon Titan. After Cassini’s surprising discovery of a towering plume of icy spray in 2005, emanating from hot cracks near the south pole, scientists turned its detectors toward the small moon.
Cassini wasn’t designed to detect signs of life in the Enceladus plume – indeed, scientists didn’t know the plume existed until after the spacecraft arrived at Saturn.
“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” said Hunter Waite, lead author of the Cassini study.
The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea; the new findings support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.
Boolean logic
How to program in Scratch, using Boolean logic
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Boolean operators include:
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AND, OR, NOT, < , = , >
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In other words, is one sprite touching some other thing? The answer by definition must be true or false.
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In other words, is one sprite touching something of a certain color? The answer by definition must be true or false.
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In other words, is a certain key being pressed?
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In other words, is the mouse being used?
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Why use Boolean operators?
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To focus a search, particularly when your topic contains multiple search terms.
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To connect various pieces of information to find exactly what you’re looking for.
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https://sites.google.com/a/onalaskaschools.com/tech/boolean-search-tools
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https://ircutp.wordpress.com/utp-irc-faqs/boolean-operators/
A Boolean block is a hexagonal block (shaped after the Boolean elements in flowcharts)
The block contains a condition. The answer to the condition will be either true or false.
It’s important to determine if a statement (expression) is “true” or “false”.
Ways to determine TRUE and FALSE are prevalent in all kinds of decision making.
A mathematically precise way of asking if something is TRUE or FALSE is called a Boolean operation.
It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century.
Boolean data is associated with conditional statements. For example, the following statement is really a set of questions that can be answered as TRUE or FALSE.
IF (I want to go to a movie) AND (I have more than $10) THEN (I can go to the movie)
We can combine several “boolean” statements that have true/false meaning into a single statement using words like AND and OR, and NOT).
“If I want to go to the movie AND I have enough money, then I will go to the movie.”
BOTH conditions have to evaluate to true (have to be true) before the entire expression is true.
Some terms you already learned in math are really Boolean operators
Less than < [ ] < [ ] > Equal to < [ ] = [ ] > Greater than < [ ] < [ ] >
For example: (The height of a building) < 20 meters
For any building we look at, this statement will either be true or false.
Go through what each Boolean block does (page 68)
External links
Boolean: Lesson 13: GetCoding
Books
Book “Adventures in Coding”, Eva Holland and Chris Minnick, Wiley, 2016. Pages 50-59
Learning Standards
Massachusetts
Computational Thinking 6-8.CT.c.2 Describe how computers store, manipulate, and transfer data types and files (e.g., integers, real numbers, Boolean Operators) in a binary system.
CSTA K-12 Computer Science Standards
CT.L2-14 Examine connections between elements of mathematics and computer science
including binary numbers, logic, sets and functions.
CPP.L2-05 Implement problem solutions using a programming language, including: looping behavior, conditional statements, logic, expressions, variables, and functions.
Bullet spin angular momentum
How can we see a bullet’s angular momentum?
Video of a bullet spinning on ice: angular momentum is conserved
Video of a bullet spinning on ice #2 , http://gif-finder.com/bullet-spinning-on-ice/
Spinning bullet on ice. Long video
Mythbusters tested this claim in episode 166 – “Spy Car 2”, May 18, 2011
Myth Statement: A bullet fired into the surface of a frozen lake can spin like a top on impact. Inspired by a viral video.
MythBusters: Give bullet room to bounce – clip
How does a bullet start spinning to begin with?
Guns are rifled in order to impart spin to a bullet leaving the barrel.
Rifling gives the bullet angular momentum, which stabilizes it
(keeps it from tumbling)
New articles
A sudden decision to aim a handgun at some Houston County ice in 2003 yielded a video of spinning bullets that became an Internet sensation and led to a May 18 appearance on cable television’s “Mythbusters” show. The “myth” was born on a winter afternoon when Nate Smith of La Crescent, Minn., along with friends Nate and Andy Van Loon, were shooting bullets from a 9-mm Glock from a hillside toward a patch of ice on the Van Loons’ land near Houston.
“We just went out, not being very smart, and were shooting the ice and watching the pieces of ice fly, and we were recording ourselves,” Smith said. “I remember, after we shot a couple times, wondering what that crackling sound we were hearing was.”
After firing multiple shots, they found the bullets spinning on end on the ice surface, a few feet back from the point of impact. “You could see the trail from where it ricocheted and that’s how we found it,” Smith said. “And it went for about two minutes, so we just filmed that.”
The only explanation Smith could offer is rifling in the gun barrel caused the bullets to spin. Though Smith first put the video on the Internet in 2005, it took off in December 2009 when Smith’s friend Jason Nesbit asked if he could re-post it on YouTube. More than a half-million people have since viewed it.
When questions arose over the validity of the clip, Nesbit asked if he could re-create it on a local frozen lake. “We didn’t think anything would happen, so we said, ‘Sure, go ahead. Do whatever,'” Smith said. But Nesbit went further, sending the video to the “Mythbusters” website, where it caught the attention of the Discovery Channel show’s producers. Smith and Nesbit also were contacted by an Asian television show that paid them a small stipend to use the video. Smith watched May 18 as the “Mythbusters” hosts worked to prove or disprove what he had seen with his own eyes. “Somehow, they get their bullets to just spin like a top,” host Kari Byron said on the show. “Now that sounds like a myth,” co-host Tory Belleci added.
The key element was finding the correct angle to fire the gun into the ice, Belleci said. Too straight would deform the bullet too much to spin, too shallow would send the slug skipping off the ice.
The hosts set up nine 40-by-24-by-10-inch chunks of ice next to each other to replicate the frozen lake. The first shots became embedded in the ice and had no chance to spin. But a bullet was recovered that hadn’t deformed, a cause for cautious optimism. Yet the next several tests failed to yielded a spinning bullet, so the hosts tried firing at an angle to ricochet off a large piece of ice between 2 and 8 feet away from the initial contact point. The hit was clean, but the bullet was gone. Several more tries, several more lost bullets. The hosts decided to try again six months later on an actual frozen lake. But shot after shot and no luck. “This myth sucks,” Belleci said in the blizzard-like conditions.
For the final test, they gave the bullet room to ricochet backwards, as it had on Smith’s outing. After countless attempts, they found the spin they were looking for. It happened again and again, confirming the myth. Smith said the whole experience was somewhat surreal, since he once joked the video might someday make it to “Mythbusters.” “Eight years later, here we are and it was on TV,” he said. But he doesn’t recommend anyone try this at home. “Looking back at it,” he said, “it wasn’t very safe.”
- article from Lacrosse tribune. ‘Mythbusters’ tackles Houston County video of spinning bullets. By Ryan Henry, Houston County News
Fair use
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Bullet spin kinematics
If a bullet is fired straight up in the air, will it return to ground level with the same velocity?
Some labs are not safe to perform in schools, but give valuable insight on physics: Thus we may watch a video of such an experiment.
MythBusters Episode 50 – “Bullets Fired Up” – Busted, Plausible, and Confirmed
All guns are “rifled” in order to impart spin to a bullet leaving the barrel.
This rifling gives the bullet angular momentum, which stabilizes it (keeps it from tumbling)
How can we see a bullet’s angular momentum?
Video of a bullet spinning on ice: angular momentum is conserved
Video of a bullet spinning on ice #2 , http://gif-finder.com/bullet-spinning-on-ice/
Rhett Allain offers a physics analysis of the “Bullets Fired Up” episode of MythBusters
http://kwc.org/mythbusters/2006/04/episode_50_bullets_fired_up_vo_1.html
Summary of results: Bullets Fired up
Annotated MythBusters: Bullets Fired Up analysis
Analysis: Bullets Fired Up – MythBusters
Results are complicated: In most cases the bullet lands with non-lethal velocities, despite confirmed cases to the contrary. How to solve this apparent paradox?
There are really two different cases:
Experiments show that bullets lose (*) spin (and angular momentum) via interactions with the air. Once they lose angular momentum they are no longer spin-stabilized. Without spin-stabilization they tumble, and thus they experience more drag (“air resistance”), slowing them down more.
Bullets fired at an angle can come back down fast enough to kill someone. Experiments show that this allows bullets to keep more of their spin/angular momentum. They stay spin-stabilized for more of the trajectory, and thus keep more of their energy upon landing.
(*) Both momentum and angular momentum are conserved quantities; when we say that an objects loses either, it is because the momentum is actually transferred at a microscopic level to the surrounding molecules of air. See our lesson on momentum.
Analysis: What if the bullet falls without tumbling? How fast would they go
PhysicsForum meber WhyIsItSo gives us the following:
In the original post, there was not sufficient information to say, for example, if the bullet still had kinetic energy from being fired, or if all the speed that was left was its terminal velocity. For the latter case – Assumptions:
1. Take the ideal case (unlikely) that the bullet is falling in a consistently “nose-down” attitude.
2. Air pressure is 1.29Kg/m^3
3. Use a .45 Cal bullet, mass 300 g, drag coefficient 0.228. The “nose down” attitude gives us a cross-sectional area of 0.0001026m2.
4. Still day [no winds].
5. Ignoring humidty.
Process: We can use the Quadratic drag formula.
m = mass of bullet
g = acceleration of gravity = 9.8 m/s2
C = drag coefficient
ρ = air pressure [This symbol is the Greek letter rho]
A = cross-sectional area of bullet
That comes out to about :
Velocity terminal = 442 m/s = 1,448 ft/s = 987 miles/hour.
Gun enthusiasts are probably thinking that number is higher than the muzzle velocity of most guns, which means that in this “ideal” scenario, a bullet fired straight up wouldn’t get high enough to attain terminal velocity on the way down.
Much more realistic would be to assume the bullet is more or less sideways on the way down. This will result in a drag coefficient more like 0.6 (a sphere is about 0.5), and a cross-sectional area – very roughly – twice the nose-on area, or say 0.0002052 m2
Plugging those numbers in gives:
Velocity terminal = 192 m/s = 630 ft/s = 430 miles/hour
Reference https://www.physicsforums.com/threads/how-fast-does-a-bullet-return-to-earth.14560/
How fast does a bullet return to Earth?
Ray Tracing
This lesson is from Rick Matthews, Professor of Physics, Wake Forest University.
Lesson 1, convex lens: The object is far from the lens.

Lesson 2, convex lens: The object is near the lens

The rules for concave lenses, are similar:
A horizontal ray is refracted outward, as if emanating from the near focal point.
A ray that strikes the middle of the lens continues in a straight line.
A ray coming from the object, far from the far focal point, will leave the lens horizontal.
Lesson 3, concave lens.
Note that object placement has little effect on the nature of the image: The rays diverge.

In every case:
…if the rays leaving the lens actually intersect then the image is real.
… if the rays leaving the lens diverge then someone looking back through the lens
would see a virtual image:
Your mind extrapolates where you think the image should be, even though one isn’t really there, as shown below with the dotted lines.

image from Giancoli Physics, 6th edition
http://users.wfu.edu/matthews/courses/tutorials/RayTrace/RayTracing.html
PhET Electric circuit lab
An electronics kit in your computer! Build circuits with resistors, light bulbs, batteries, and switches. Take measurements with the realistic ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a life-like view.
Learning Goals
- Discuss basic electricity relationships.
- Build circuits from schematic drawings.
- Use an ammeter and voltmeter to take readings in circuits.
- Provide reasoning to explain the measurements and relationships in circuits.
- Discuss basic electricity relationships in series and parallel circuits.
- Provide reasoning to explain the measurements in circuits.
- Determine the resistance of common objects in the “Grab Bag.”

PhET Circuit construction kit lab!
Start with “grab a wire” – Pull a “wire” onto the screen.
Add resistors, at least one battery, a lightbulb and a switch.
Move the elements close together, so they connect.
If you need to break 2 pieces apart, right click at the location, and choose ‘split junction’
a) Create a series circuit with one light bulb that you can turn on/off.
Click ‘voltmeter’ and a virtual voltmeter appears on the screen. Move the voltmeter’s leads.
When the switch is off
1) measure the voltage across the bulb : _____
2) measure the voltage across the battery: _____
Then with the switch on, do this again.
b) Create a parallel circuit with 2 bulbs that you can turn on/off
Click ‘voltmeter’ and a virtual voltmeter appears on the screen. Move the voltmeter’s leads.
When the switch is off
1) measure the voltage across bulb A : _____
2) measure the voltage across bulb B : _____
3) measure the voltage across the battery: _____
Then with the switch on, do this again.
Geekiness and autism: Is there a connection?
02:58 PM ET
Geekiness and autism: Is there a connection?
Elizabeth Landau
http://geekout.blogs.cnn.com/2012/04/23/geekiness-and-autism-is-there-a-connection/
Laura Nagle loves physics. She peruses scientific papers for her own enjoyment, and she can sometimes work out the answers to cosmological mysteries in her head when she watches documentaries about the universe. She has read, in her estimation, about 12,000 books.
You might say Nagle, 58, is a geek. But if you knew that she also has had severe problems communicating with others throughout her life, and had trouble in school because she’s not “well-rounded,” you might guess that she also has autism.
“I find that physics, engineering – these things speak to my heart, and I see details, relationships and patterns that most people don’t,” says Nagle, who lives near Flagstaff, Arizona.
Nagle’s experience speaks to a pervasive stereotype in popular culture that people with high-functioning autism – a form of which is called Asperger’s syndrome – are geeks.
As with most generalizations, it excludes a vast swath of people on the autism spectrum who don’t fit it – plenty have interests or talents in the arts or literature, and don’t care at all about traditionally geeky pursuits such as computers, science and technology.
But it’s worth looking at why this image of the geek with autism has emerged, and exploring the realities of how autism and talent intertwine. Understanding the condition better is ever more important as the number of people with autism rises. The main signs and symptoms of the condition are communication problems, poor social interactions and repetitive behaviors.
Just last month, the Centers for Disease Control and Prevention announced that an estimated one in 88 children in the United States have an autism spectrum disorder. A person who has high-functioning autism and did not have a childhood delay in cognitive or language development would get a diagnosis of Asperger’s syndrome, although this distinction is likely to disappear in the next edition of the Diagnostic and Statistical Manual of Mental Disorders, the standard classification of mental disorders used by mental health professionals in the United States.
Diagnosing genius
While more and more American children are found to have an autism spectrum disorder, speculation has abounded about brilliant historical figures and fictional characters having it, too.
Albert Einstein and Isaac Newton, both fundamental in shaping the way we understand the universe, had characteristics of Asperger’s, researchers have postulated.
Then there’s TV – take Sheldon Cooper, a character from “The Big Bang Theory.” (Although the show’s writers have said that the character does not have Asperger’s syndrome, actor Jim Parsons told Variety that he views his role as in line with the condition.) And people with Asperger’s have connected with the quirky behaviors of Dr. House from “House, M.D.” and Temperance “Bones” Brennan of “Bones,” although these characters have not received formal diagnoses. (For that matter, another doctor on “House, M.D.” once concluded that House is simply a jerk.)
All of these characters seem obsessed with scientific inquiry, but they struggle with effective communication or maintaining relationships. (Not to mention Abed from “Community” – he’s got an encyclopedic knowledge of science fiction, but asked in a recent episode, “Is this a social cue?”)
“[Viewers] could look at any of these characters who are ostensibly Aspies, and they could think that we have no passion because sometimes our language doesn’t seem to convey deep emotions, and we are doing things that most people do not seem to find inspiring of passion,” Nagle said.
And Nagle doesn’t mind that the public associates genius characters with autism – to her, they represent an idea she’s passionate about: That there’s room in this world for everyone, regardless of their quirks and social deficits.
“You get this idea that even if Sheldon is not a party guy, even if Sheldon is not the guy you’d want to have trying to repair your car, that maybe it’s important to have a theoretical physicist or two,” she said.
Others say the stereotype of the Asperger’s scientific genius is unfortunate; that it overshadows the fact that many people with high-functioning autism have talents in arts and literature instead, says Teresa Bolick, a licensed psychologist who specializes in neurodevelopmental disorders. And some are not geniuses per se, they are simply fixated on specific interests.
In other words, not all smart people have Asperger’s, and not all people with Asperger’s have great talents. The diagnosis requires that the person have some kind of social impairment – for instance, lack of eye contact, and not being able to interpret facial expressions, gestures and figurative speech. So a physics genius who gets along well with everyone may well not have autism.
A genetic basis for both scientific talent and autism?
There may still be an underlying connection between scientific talents and autism, however.
More study is needed to back up this theory, but one hypothesis is that geeks and people with autism are linked genetically. British autism expert Simon Baron-Cohen and colleagues published a study in 1997 suggesting that fathers and grandfathers of children with autism were more likely to work in the field of engineering, compared with fathers and grandfathers of neurotypical children.
The researchers are expanding upon their study to see if people who are good at computers and science are generally more likely to have a child with autism.
“One possibility is that the very same genes that give rise to autism, in a less severe combination, might also be giving rise to talent in the general population,” said Baron-Cohen, who is a first cousin of the comedian and actor Sacha.
A larger combination of those genes could give rise to more severe forms of autism, Baron-Cohen speculated. And it could be that people who carry those genes, being similar in personality and interests, have a greater likelihood of marrying each other.
“If you were to get rid of all the autism genetics, there would be no more Silicon Valley,” Temple Grandin, a best-selling author and professor of animal science at Colorado State University, who has autism, said in a TED talk in 2010.
Although these ideas have gained traction, they aren’t based on proven scientific facts; further research is necessary to support these conclusions.
And keep in mind that as awareness grows about autism, doctors have realized that intellectual disability in autism is nowhere near 70%, as was previously thought – it’s only around 30%, Dr. Gary Goldstein, president of the Kennedy Krieger Institute, told CNN.
A darker side of the stereotype
Meanwhile, the false notion that all people with high-functioning autism are talented in the sciences persists culturally – and that may have a detrimental effect on parents.
“Many of us in the autism community, with official diagnoses, are often asked ‘What’s your special science ability?’ says Christopher Scott Wyatt, assistant professor of English at Robert Morris University. “I say, ‘I teach poetry.’ ”
When speaking about autism, Wyatt, who has high-functioning autism, often fields questions from parents of children on the spectrum who wonder when they will see a math or science ability come through. The answer is: Many children don’t have it. The stereotype of the geek with autism has this downside of making parents concerned if their children with the condition don’t excel at science.
“It leads to assumptions of magical abilities,” he said. “They’re expected to have traits they don’t have.”
Gretchen Leary, 26, of Boston, has Asperger’s syndrome and, like Wyatt, her passion is for writing, not the physical sciences. She also has other narrowly focused interests, such as Latin and marine biology. But although she’s not a tech geek per se, her job involves data entry and other repetitive tasks that appeal to her cravings for order and familiarity. See her iReport
Nagle also has particularities about things that are familiar – if you want to kick her out of a room, “paint it lavender,” she says.
So what is the difference between being a geek and having Asperger’s?
Experts are quick to point out that autism is a medical diagnosis, and “geek” is not – of course.
And in order to receive a diagnosis, a person must see a doctor, probably because he or she is suffering in some way. Being a geek is a cultural description, not a medical condition.
People with high-functioning autism may become depressed because they are failing at relationships or jobs, or anxious because of their social interactions. They may have severe difficulties communicating with other people that have led to troubles at home or the workplace. Leary says she’s had many misunderstandings with her spouse and still has more trouble with face-to-face communication than via phone.
Sensitivity to light and noise, another common feature of autism, has also been problematic for Leary. These sensory issues can also interfere with children’s socialization. Crowded, bright places like shopping malls, where young people often hang out, can feel overwhelming and isolate those who don’t want to be there, said Bolick, the psychologist.
Underlying the interests of many people with Asperger’s is a fascination with systems, Baron-Cohen said. Sometimes, that can be advantageous and could help start careers, such as in software engineering or physics. But sometimes, people who have autism fixate on activities that do not have immediate practical applications – for instance, collecting coffee cups.
“Many folks with Asperger’s are able to give remarkable attention to whatever problem they’re interested in,” Bolick said.
Turning a disability around
In some cases, people on the autism spectrum have talents or interests that could become part of a profession, but they’re not thinking in those terms.
“For many people with autism, the reason why they have their obsessions is not because of financial gain. They’re doing it because of intrinsic motivation,” Baron-Cohen said. “The idea that they could make it useful may not even occur to them.”
Wyatt, for example, writes a lot but doesn’t publish. “My wife keeps saying, ‘You should send this to someone,’ but why?” he says.
One man with Asperger’s whom Baron-Cohen met had a desire to understand changes in weather patterns. He’d go out into his garden at midnight every night to measure temperature, wind speed and other related weather factors. He wasn’t trying to use the information like a meteorologist; he just wanted to know.
Similarly, a young patient of Bolick’s would diligently do his homework but not turn it in. When she asked him about it, he stood straight up and said, “I don’t do my homework to get good grades. I do my homework to learn.”
But this problem of not finding practical uses for interests varies widely; some people with autism are markedly driven to achieve, and do. Other times, success is hindered by difficulty in planning and organizing, another common feature of autism spectrum disorders. These are areas that teachers and coaches can help with, Bolick said. Grandin has also spoken out about the need for these mentors to help people with autism develop their talents and use their interests in meaningful ways.
And organizations are starting to take note of certain strengths that a person with high-functioning autism might bring. The nonprofit Aspiritech, based in Highland Park ,Illinois, provides opportunities for people on the Asperger’s spectrum to become software testers, a profession that harnesses their “attention to detail, precision, an affinity for repetitive tasks, outstanding technology skills.”
“This is the kind of disability which could be turned around, so that something that seems to be interfering with the person’s life could transform their life,” Baron-Cohen said. “The obsessions could be a stepping stone or a passport into more opportunities.”
Toward a better future for the next generation
Doug Sparling, 52, of Kansas City, Missouri, chose his job in software engineering because of his Asperger’s. Human interaction, especially when working on a project closely with a partner, can trigger anxiety for him. But he loves electronics, logic and solving problems.
In information technology, he can follow those passions while largely having the solitude he wants. He works more than 40 hours a week, but on a flexible schedule, and works from home a lot.
“Coding is something I get ‘lost’ in, it’s a world where I lose track of time,” he said in an e-mail.
Sparling is married with four children, including a 23-year-old stepson and a 12-year-old son with Asperger’s.
Nagle’s story is different. If she’d had supportive, encouraging teachers, coaches or advocates, Nagle believes, she would have turned her passion for physics into a career, too.
During her second year of college, a counselor told her that her grant would be cut and her work-study hours cut in half. And instead of questioning it or investigating other scholarship opportunities, she quit school and began one of many jobs she didn’t enjoy.
She has worked in architecture and structural engineering, but never finished college. She now lives in a mobile home provided to her. She is heavily involved in autism advocacy and is working on a documentary to be released this year.
When Nagle gives talks about autism, she tells her audience she hopes that none of the young people with autism today end up like herself.
She says: “I don’t want them being 58 years old, homeless [if not for] favors, not able to take care of their teeth, and looking back on lives in which they haven’t accomplished what they could have accomplished.”
See our article on issues relating to Asperger syndrome and Autism
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