184_projects:railgun_24 [Projects & Practices in Physics]

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===== Project: EM-Boartiger Cub =====

==== Kick Off Questions ====
  - What is the right hand rule for the magnetic field from a current-carrying wire? What is the right hand rule for the magnetic force on a current-carrying wire?
  - Suppose you have a single straight wire with a current. That current will create a magnetic field. Will that magnetic field exert a force back on the current? Why or why not?
  - Way back from Physics 1 - how does velocity relate to acceleration? How does acceleration relate to force? What is a net force?

==== Main Problem ====

With the power line rebuilding underway, Director Lewis calls.  She says that Dr. McPaddel was working in her junkyard before everything went crazy in Lakeview last night.  A mysterious glowing creature entered the junkyard and started eating some of the scrap metal laying around.  Dr. McPaddel was using her magnetic crane at the time, and when the creature wandered too close it got pulled up into the air and remained stuck to the crane until this morning.  When Dr. McPaddel alerted the authorities, they asked the FTOE researchers for help.

By the time you learn of all this, the creature is already at the research facility. You arrive and the scientists fill you in - the creature has large tusks like a boar but striped fur like a tiger's.  Because of that and the weird blue electromagnetic glow it's emitting, they're calling it an EM-boartiger.  By now they have figured out Dr. McPaddel's crane snagged a young version of the monster, so you have captured an EM-boartiger cub. 

Just then, the herd of EM-boartigers arrive and organize to attack the lab.  Surprisingly, even though it is a secret government facility, there are no weapons at the compound, not even a flamethrower!  You realize that capturing the young of this new 'alien' species must 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 usies magnetic force to launch projectiles so that they will leave the launcher at a speed of $300 \;{\rm m/s}$. 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. Finally, you have access to multiple variable power supplies that can be set to provide a requested current, 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 $300 \;{\rm m/s}$.

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

<WRAP Info>
=== Learning Goals === 
  * Use resources (internet, whiteboards, etc.) to draw out and understand how a rail gun works
  * Understand how superposition of magnetic fields works and practice adding magnetic fields together
  * Relate magnetic fields to forces and use those forces to calculate motion
  * Review some basic kinematics concepts - net force, acceleration, velocity relationships
  * Find the net force on an object & draw a free body diagram
  * Practice building complex models using assumptions and approximations to simplify
</WRAP>

==== Wrap Up Questions ====
  - In this scenario, you used the F = integral I dL x B equation. In particular, what current/lengths did you pick? What is making the B-field? The force that you found is the force //from// what //on// what?
  - There are a couple key assumptions you need to make about the B-field in this problem. What assumptions did you need? Why did you need them? How realistic are those assumptions?
  - What steps did you take to solve this problem?
  - What size of current did you end up finding for the problem? Is it big/small/normal? How would that impact the practical use of railguns?
  - Make a summary of the equations that we've talked about in class so far (field & force for point charges & currents). What is similar about the equations? What is different about the equations? When are each of the equations applicable?