course_planning:184_projects:f18_project_9 [Projects & Practices in Physics]

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===== Project 9 =====
==== Project 9A: EM-Boar Tiger Cub ====
Dr. McPaddel woke up to a great surprise this morning when she walked outside to admire the junkyard and noticed a mysterious glowing creature stuck to her magnetic crane. Apparently, in all the excitement of showing the contraption to her neighbors, she had forgotten to turn off the machine. The creature had wandered into the scrapyard overnight looking for some metal to eat, and when it wandered near the crane, the metal became magnetized and pulled the creature up into the air, where it remained stuck until Dr. McPaddel discovered it this morning. She alerted the authorities, but it was the Hawkion researchers who arrived before anyone else, to transport the creature to a research facility to learn more about it. They are thinking these animals might be responsible for the disappearance of fish from the lake and green-bellied canaries from the cliffside.

By the time you learn of all this, the creature is already at the research facility. You arrive and the scientists fill you in. They have acquired this beast to study it, but by now they have figured out Dr. McPaddel's crane snagged a young version of the monster. Because of the apparent resemblance to both boars and tigers and their electromagnetic glow the scientists at the compound have taken to calling the monsters EM-boar tigers. So you have captured an EM-boar tiger cub. It turns out that EM boar tigers are super protective of their young and they have organized to attack the Lakeview compound. Surprisingly, even though it is a government facility, there are no guns at the compound. But you are scientists and engineers godammit! You indicate that maybe capturing this new 'alien' species young might have upset the creatures and make a plan to return the beast but you need a distraction to get the cub close enough to give back to its kin.

You decide to construct makeshift launcher that is using magnetic force to launch projectiles so that they will leave the launcher at a speed of $300m/s$. You must construct your launcher on the floor of the laboratory and position it at an angle of 63 degrees so that it is firing out of the window of the laboratory. 

At your disposal to construct your launcher, you have access to two copper rails that can be cut to your specifications. You also have perspex that you can cut to any dimensions and chunks of aluminum that can be cut to any shape. You also have access to multiple variable power supplies that can be set to a requested current and a bunch of wires that can be cut to any length and some switches. You must outline your design, explaining the physics behind the design of the magnetic force launcher and indicating the current needed to reach an exit velocity from the launcher of $300m/s$.

{{ 183_notes:caged.jpg?700 }}

==== Project 9B: Need for Speed ====
Thanks to the research that folks at the Hawkion facility were able to do on the EM-boar tigers, the people of Lakeview have been able to set up a scientifically supported protection system. The research team has found that magnetic fields repel the EM-boar tigers. They have installed a giant magnet into the cliffs nearby, and it is aligned in such a way that there is a constant (practically speaking) $5 \text{ mT}$ magnetic field directed into the ground near Lakeview and the surrounding area. The hope is that the field will ward off the EM-boar tigers and keep the people of Lakeview safe.

However, there is a dilemma that has emerged. Local inventor and superstitious person Manny Hallabero is starting to create a fuss around town because he believes the magnetic field is going to destroy his car. He has been driving around with a voltmeter attached to his engine and he claims there is a potential difference across the engine when he's driving fast. Once, he said, there was a potential difference of $0.15 \text{ V}$. He is worried that if the voltage across his engine reaches much higher, it will surely be destroyed and he could end up in danger. Out of the goodness of your heart, you wish to assuage Manny's worries and explain to him why the potential difference exists. You should also provide some guidelines for Manny to make sure he doesn't cause the potential difference to exceed $0.15 \text{ V}$.

{{ 184_notes:12b_engine_voltmeter.png?700 |Manny's Engine}}

<WRAP info>
=== Learning Goals ===
  * Explain microscopically why there would be a potential difference across the engine
  * Use electric and magnetic forces to relate electric and magnetic fields
  * Use the right-hand rule to find the direction of the magnetic force
  * Relate electric field to the electric potential
</WRAP>