# The Physics behind “Angry Birds”

Photo credit: https://d1guvqt7k9h5xe.cloudfront.net/AcuCustom/ Sitename/DAM/005/red_400x400.jpg

by Emily Lehman and Meghan Nay

We are avid Angry Birds fans, so when our physics teacher offered us the opportunity to analyze the validity of physics principles underlying the game, we accepted eagerly. We conducted an analysis to determine whether the mobile application “Angry Birds” followed the principles of physics – specifically, principles of projectile motion.

We videoed the game from the initial launch of a bird to his collision with the pig pedestal. Then, we used Tracker software to collect data of the bird’s motion. Here’s our procedure:

1) We uploaded the video of the red angry bird into the software,Tracker.

2) Using Tracker, we found the horizontal and vertical position vs. time graphs. From there, we found the equation of the best fit line/curve.

3) After obtaining the equation of best fit for the position vs. time data, we took the derivative in order to find the velocity vs. time equation.

4) Then to find the acceleration vs. time equation, we took the derivative of the velocity vs. time equation.

5) Using the position, velocity, and acceleration equations, we were then able to analyze the bird’s motion and compare it to the laws of projectile motion on Earth.

6) Since we don’t know any of the measurements in the video, we established an arbitrary unit of length using the pig pedestal in the video. All equations are based on a unit of length we have called a “pig pedestal.”

Data and Analysis:

Position vs. time data using Tracker. The straight line is the horizontal position vs. time, and the concave-down parabola is the vertical position vs. time.

The graph above shows the position of the bird in the x and y directions. The best fit line for the graph in the y direction is the equation y = -1.882t² + 6.833t + 1.993. To find the velocity of this position graph we took the derivative and found the equation of the velocity in the y direction to be v = -3.764t + 6.833. Also, to find the acceleration in the y direction we found the derivative of the velocity equation and found the acceleration in the y direction to be a=-3.764 pig pedestals/s².

We repeated these steps to find the equations of the position, velocity, and acceleration graphs in the x direction. Which in subsequent order the equations of these graphs are x = 4.637t – 0.0668, v =4.637 pig pedestals/s, and a = 0 pig pedestals/s².

X-Direction

Position vs Time: s(t) = 4.637t – 0.0668

Velocity vs Time: s'(t) = v(t)= 4.637 pedestals/s

Acceleration vs Time: s”(t) = v’(t) = a(t) = 0 pedestals/s²

Y-Direction

Position vs Time: s(t) =-1.882t² + 6.833t +1.993

Velocity vs Time: s'(t) =v(t) =-3.764t + 6.833

Acceleration vs Time: s”(t) = v'(t) = a(t) =-3.764 pedestals/s²

We assumed that the Angry Birds game takes place on Earth where the acceleration due to gravity is -9.8 m/s². Using the vertical acceleration from the best fit line, we  set -3.764 pig pedestals/s2 equal to -9.8 meters/s2  which determined the height of the pig pedestal to be 2.603 meters.

Conclusion:

Based on our findings, we were able to determine that “Angry Birds” follows the rules of physics for a number of reasons. The acceleration of the bird in the x direction was zero, which is characteristic of an object launched as a projectile on Earth, assuming no air resistance. Also because the position vs. time graph in the y direction closely followed the kinematics position equation, we determined that the Angry Bird is subject to a gravitational force.

We also made some strange or odd discoveries about the game. Using the unit conversion discussed in the Analysis section, we found that the actual size of an Angry Bird is 1.019 meters tall, which is around 3.3 feet. We derived this number from the position vs. time graph in the y direction. We found the acceleration to be -3.764, but this was not meters/second2; the units for this was pig pedestals/second2. By assuming gravity in “Angry Birds” was -9.8, we used conversions to find the height of the pig pedestal. Then, we were able to find the height of the bird, which was 1.1019 meters. Certainly, a bird of this size would be subject to air resistance; however, the data show no force in the horizontal direction!

Photo credit: http://resources0.news.com.au/images/ 2012/09/16/1226475/242180-rheinmetall-039-s-simulators-in-use.jpg

Determining that one video game followed the rules of physics on Earth opens up many possibilities for real world applications. Virtual simulations have the potential to revolutionize society and many fields of work. For example, virtual simulations are extremely helpful in pilot training or training for warfare. The analysis that we undertook could be used to assess the validity of these simulations and thus gauge their acceptability as effective training tools.

By kimgeddes

# Energy Explorations with Rube Goldberg Machines

## Rube Goldberg Toaster

When challenged to design a series of energy transformations that ultimately perform a task, these students devised a clever method of making toast. They began with a diagram of their system:

And, here’s the final product. Great job guys!

By kimgeddes

# Harvesting the energy from friction to create a safer bike

by Dalton Mullinax,  Jonathan Guy, Ryan Koprowski, and Matthew Laczko

Photo credit: static.environmentalgraffiti.com

Today, biker safety is often overlooked because many adults travel by car; however, young people without a driver’s license routinely rely on bicycles to travel short distances. For this reason, we wanted to find a way to increase the safety for bicyclists. Lights, being the predominant method of visibility, are absent on many bikes. For our project, we sought to improve biker safety by being able to power the lights on a bike using the friction that exists between the tires and the road. If we could harvest the energy lost due to friction, we could power the lights on the bike, thus improving biker safety.

We propose constructing bicycle tires with polyester-PDMS fiber interwoven within the fabric of the tire. The recent understanding of PDMS with polyester has opened a new door to the realm of attaining energy from frictional forces between two materials. This polyester-PDMS fabric is capable of generating energy from friction produced between the tire and the surface as the bicycle moves.

Today, many scientists around the world experiment with various methods to find ways to convert mechanical energy from two objects rubbing together to electrical energy. Physicists at the Georgia Institute of Technology in Atlanta, Georgia have found use in the triboelectric effect which is when two plastics rub together to create friction that can be harnessed by a triboelectric generator. These triboelectric generators are composed of smaller generators called nanogenerators that aid in the production of electrical energy (Toon). Although these triboelectric generators are small, the polyester piece rubs against a polydimethysiloxane (PDMS) sheet, thus creating friction that can be converted into electrical energy.

One form of this triboelectric generator is the PENG device, which is shown to the very far left in the picture below (Zyga).  This device has been proven to power the LCD screen, shown in the middle of the picture below, for upwards of one minute. Also, the PENG device has partially charged a lithium-ion battery (the image on the right in the picture) (Zyga).

The triboelectric generator uses the Piezoelectric Effect; “the piezoelectric substance is one that produces an electric charge when a mechanical stress is applied” (“Piezoelectric Effect”). The piezoelectric effect happens when a crystal acquires a charge when it is twisted, compressed, or distorted. One of the most useful characteristics of the piezoelectric effects is that is can be reversed easily (“The Piezoelectric Effect”). The figure below shows the forward and reverse motion of the piezoelectric effect.

When the piezoelectric effect material is stressed in forward motion, positive and negative particles shift which helps create an electrical field that can be harnessed through a nanogenerator. But, when the material is reversed, the electrical field does the exact opposite of the forward motion and uses an electrical field to create the piezoelectric effect material which then can be reused to make the forward motion.

Through our design, we are taking a new step toward nanotechnological use of a polyester-PDMS inner ring: we propose constructing bicycle tires with polyester-PDMS fiber interwoven within the fabric of the tire. This polyester-PDMS fabric will generate energy from friction produced between the tire and the surface as the bicycle moves.  This energy will be harvested and transmitted through a cable attached to the axle of the wheel and terminated at a connection on the handlebars of the bike. This terminal connection will then provide energy to the LED lights on the bicycle.

The picture below demonstrates the use of a PDMS with a rubber surface that can be used to create energy by touch. The inset picture shows that even the touch of a feather could set the sensor off and create energy as well as power the device through a triboelectric generator. This picture illustrates the device we will use in the rubber tires of the bicycle and demonstrates how the triboelectric generator will use friction to produce electricity to power the bicycle’s safety lights.

Photo Credit: Zhong Lin Wang, Triboelectric generator

Our idea is to put the sheets of PDMS and polyester into the interior of the bike’s tires. One sheet would rotate with the movement of the bike and the other would rub the other way with the use a counter-rotating piece also in the interior of the bike’s tires. As the bike is ridden, friction would be created between the PDMS and polyester sheets rubbing together. The triboelectric generator would capture this energy so it could power the lights on the bike. Assuming technology is developed that shows how the energy consumed into the triboelectric generator could be released, this new technology could immensely increase biker safety.

Lights added onto a bicycle will improve rider safety and also increase the safety of car drivers around the biker. More bikers will be able to travel at night because their visibility will be increased, allowing their confidence in riding at night to be greater. Plus, all the light energy produced by triboelectric generator is environmentally friendly.

References

Fan, Feng-Ru, Zhong-Qun Tian, and Zhong Lin Wang. Flexible Triboelectric Generator! Atlanta, GA: Sciverse Science Direct, 10 Jan. 2012. PDF.

Hum, Phillip W. “Exploration of Large Scale Manufacturing of Polydimethylsiloxane (PDMS) Microfluidic Devices.” Diss. Massachussets Institute of Technology, 2006. Abstract. (2006): 1-56. Print.

“The Piezoelectric Effect.” Nanomotion Piezoelectric Effect. Nanomotion, n.d. Web. 03 Dec. 2012. http://www.nanomotion.com/piezoelectric-effect.html.

“Piezoelectric Effect.” Piezoelectricity. GSU, n.d. Web. 03 Dec. 2012. http://hyperphysics.phy-astr.gsu.edu/hbase/solids/piezo.html.

Quick, Darren. “Triboelectric Generator Could Allow Electricity-generating Touchscreens.” Triboelectric Generator Could Allow Electricity-generating Touchscreens. Gizmag, 9 July 2012. Web. 27 Nov. 2012. http://www.gizmag.com/triboelectric-generator/23248/.

Sihong Wang, Long Lin, Zhong Lin Wang. Nanoscale Triboelectric- Effect-Enabled Energy Conversion for Sustainably Powering Portable Electronics. NanoLetter. Washington, DC: American Chemical Society Publications, 2012.

Toon, John. “Georgia Tech Research News.” Georgia Tech Research News RSS. N.p., 9 July 2012. Web. 27 Nov. 2012. http://gtresearchnews.gatech.edu/triboelectric-generator-produces-electricity-from-friction/.

Toon, John. “Triboelectric Generator Produces Electricity by Harnessing Frictional Forces.” GT. N.p., 10 July 2012. Web. 15 Nov. 2012. http://gatech.edu/newsroom/release.html?nid=139511.

“The TriboElectric Series.” The TriboElectric Series. N.p., 30 Nov. 2012. Web. 30 Nov. 2012. http://www.trifield.com/content/tribo-electric-series/.

Zyga, Lisa. “Pyroelectric Nanogenerator Charges Li-ion Battery with Harvested Energy.” Pyroelectric Nanogenerator Charges Li-ion Battery with Harvested Energy. N.p., 20 Nov. 2012. Web. 29 Nov. 2012. http://phys.org/news/2012-11-pyroelectric-nanogenerator-li-ion-battery-harvested.html.

# Physics merges with Biology to Keep the Heart Beating

by Julia Clark, Anna King, and Taylor Kuter

In today’s world, pacemakers are so commonplace, we hardly give them a second thought. Nearly everyone knows someone whose life depends on this device. Despite a wide variety of pacemaker models, they all have the same basic composition, and consist of the same three core parts: a battery, lead wires, and circuitry (How Pacemakers Are Made). All materials used in these parts are biocompatible, so as to be as non-harmful to the body as possible. These components all must meet a series of specifications. The circuitry of the modern pacemaker, which controls the device’s functions, contains an array of sensors, timers, and voltage regulators to control the heartbeat. All controls are generally externally programmable, allowing doctors to make non-invasive adjustments to the pacemaker’s function, if necessary. The lead wires of the device provide the physical stimulation to the heart. Leads are generally thin, insulated electrical wires with exposed ends directly attached to vital points on the heart. Many modern leads are of a “screw-in” variety, securing them to the heart in much the same way as a common screw. The wires are subjected to constant movement caused by the heart’s continuous beating, and therefore must be resistant to fracture. The battery, which powers the pacemaker, must be able to supply 5 volts of power, which is slightly more than what the heart requires for stimulation. The battery must be able to last for a minimum of four years, and must have a predictable life cycle, making it easy for the doctor to know when a replacement battery is necessary. The battery is integral to the pacemaker’s function, and must be replaced after a certain amount of time, depending on the patient. Currently, the only way of replacing the battery is through an invasive surgical procedure.

The need to undergo an operation every ten years in order to replace a pacemaker demonstrates the need for a new design of the pacemaker and how the pacemaker obtains energy. Instead of being run solely on batteries that need to be replaced, we have designed a Hematologic-Electric Pacemaker with batteries that have a back-up power supply that obtains its energy from the natural movement of blood in the patient. The purpose of our device is not to be the power source of the pacemaker but to produce enough energy from the additive that it will charge the batteries of the pacemaker. The capability of having a device that will produce the energy needed to charge the batteries of the pacemaker will eliminate the need for the replacement surgeries of pacemakers.

Our Hematologic-Electric Pacemaker will have the modern pacemaker itself and an additive that is connected by bio-compatible wire that the electrical current will run through. The additive is where the energy is created by the movement of the blood. The location in which the additive will be placed will be a vein. A section of the vein will be cut and our device added in place of the vein with skin grafts to connect the vein to the ends of the device. Stints may be needed in the vein to help support the added weight from the device. We chose the location for the device to be a vein as the pressure within the vein is low but the volume is high (Desai).

Original artwork provided by authors.

The device itself is made up of three chambers. The first inner chamber is in a shape of a barrel. Inside this barrel are propellers which are in the shape of airplane propellers. They are as if two flat surfaces lying horizontally are slightly twisted. The front propeller is made out of a harder bio-compatible material while the back propeller is made out of a more flexible material to create less turbulence in the blood as it re-enters the actual vein. As the blood from the vein travels through the barrel, the movement of the blood causes the propeller blades to spin. The shape of the propellers makes it so the blood can pass through the device freely without a large obstruction in its path. The propellers are connected to the barrel. The barrel is a magnet in which the top half of the barrel has a positive charge and the bottom half of the barrel has a negative charge. Since the propellers are connected to the barrel, the whole barrel moves as one unit. The barrel itself will be enclosed in a thin, bio-compatible membrane. Tightly wrapped around the membrane will be copper wire. To protect the body from exposed wire, the third bio-compatible casing will enclose the wire.
Our design allows the processes of electromagnetism and hematologic-electricity to occur. Electricity is “simply moving electrons” and “some metals, like copper, have electrons that are loosely held; they are easily pushed from their levels” (Intermediate Energy Infobook). The way in which our device creates electricity is similar to the turbine generators today but instead of using a substance like water to spin the turbine, the Hematologic-Electric Pacemaker uses the blood in the vein. The spinning of the barrel, or the spinning of the magnet, causes a magnetic field where the loose electrons in the copper wire, which is wrapped around the membrane of the barrel, are being pushed and pulled by the magnetic field (Intermediate Energy Infobook). The moving electrons in the wire will flow into a connected transmission line which will eventually lead to the pacemaker. There is an AC/DC converter connected to the transmission line just as the moving electrons enter into the line. Since the electrons are rapidly moving back and forth, they are moving in an alternating current. Before the electricity is able to get to the pacemaker, it needs to be transferred into a direct current. The AC/DC converter solves this issue as it converts the alternating current to a direct current so the flow of electrons is in one direction traveling toward the pacemaker.

Photo credit: Web 1/12/2012 via Creative Commons license

Once the blood is about the leave the barrel, the spinning motion of the propellers will cause the blood to leave the barrel twisting. In order to straighten out and slow down the blood flow, the membrane and the outer casing of the device is extended after the barrel. This extension of casing is called the turbulence reducing chamber. The turbulence reducing chamber solves the problem of the blood having turbulence as it leaves the device, as it allows the blood to regulate itself before it enters into the normal vein again. Inside the turbulence reducing chamber are backflow prevention valves. These valves are in place because as the blood pulses through the vein, there is an inevitable backward suction of the blood that occurs, and the backflow prevention valves make sure the blood will not re-enter into the barrel. Once the blood straightens back out inside the turbulence reducing chamber, it re-enters the actual vein.

“There are about 3 million people worldwide with pacemakers, and each year 600,000 pacemakers are implanted” (Wood, Mark A. and Kenneth A. Ellenbogen). The duration of pacemaker batteries is about 10 years, so every 10 years pacemaker patients have to undergo another surgery to replace the batteries. Our goal is to eliminate the need for replacement surgeries for the batteries of the pacemaker by our Hematologic-Electric Pacemaker.

References

Ashesh, Sheetal, Pratik, and Deeba. “History of Pacemakers.” The Physics of a Pacemaker. N.p., n.d. Web. 16 Nov. 2012.

“Benefits and Risks- Pacemakers.” Medtronic. N.p., 22 Sept. 2010. Web. 16 Nov. 2012.

“Benefits of the Advances in Cardiac Pacemaker Technology.” National Center for Biotechnology Information. U.S. National Library of Medicine. 15 Nov. 2012.

Desai, Rishi, M.D. “Arteries vs. Veins – What’s the Difference?” Blood Vessel Diseases. Khan Academy, 2012. Web. 11 Nov. 2012.

Heart Rhythm Society. “Treatment and Devices.” Treatment and Devices. Arrythmia.org, 2011. Web. 07 Dec. 2012.

Intermediate Energy Infobook. Electricity. Manassas: The NEED Project, 2012. PDF.

Laursen, Lucas. “Swiss Scientists Design a Turbine to Fit in Human Arteries.” IEEE Spectrum. IEEE Spectrum, 16 May 2011. Web. 26 Nov. 2012.

Mittal, Tarun. Pacemakers — A Journey through the Years. New Delhi: All India Institute of Medical Sciences, 10 Sept. 2005. PDF.

Rhoads, Caroline S., and John M. Miller MD. “What are some Recent Advances in Pacemaker Technology?” EMedicineHealth. 18 June 2009. Healthwise Staff. 15 Nov. 2012.

Webster, Andrew. “Scientists Create Blood Powered Turbine To Power Pacemakers.” PCMAG. Gizmodo, 17 May 2011. Web. 16 Nov. 2012.

“Who Invented the Pacemaker?” Rocket City Space Pioneers. N.p., n.d. Web. 15 Nov. 2012.

Wood, Mark A., M.D., and Kenneth A. Ellenbogen, M.D. “Cardiac Pacemakers From the Patient’s Perspective.” AHA Journals. The American Heart Association, 2012. Web. 11 Dec. 2012.

Zax, David. “A Heartbeat-Powered Pacemaker.” MIT Technology Review. 7 Nov. 2012. 16 Nov. 2012.