# Magnetic Koozie

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Stick your drink to just about any steel surface with this easy DIY Magnetic Koozie. Great for parties and tailgating and also includes some simple physics!

Materials Needed: Strong neodymium magnets, fabric, sewing materials, koozie, and a drink ;).

### Teacher Notes

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## Step 1: Choose Material--It Matters

The process is simple...get two magnets, some fabric, a koozie, and some sewing materials. We simply sewed a piece of suede onto the side of the koozie.

We chose suede because it is grippy, adding friction to the koozie. Increasing friction is crucial in making sure the koozie stays put on a vertical surface. If the fabric is too slippery, it will slide down.

Material thickness matters a lot, too. The thicker the material, the more distance between the magnets and metal surface there will be. The force of a magnet greatly decreases with distance. Keeping the material as thin as possible helps there to be more magnetic force.

## Step 2: Sew Material and Insert Magnets

After choosing our fabric, we simply sewed a strip of it to the koozie. We sewed two pockets for the magnets to sit in. We left one side open to show the magnets, but fully sew the magnets in for the best results.

We did a bunch of testing to see which magnet size would work best. With our 1/16" thick material, we found that the magnets had to be at least a 1/2" square and at least 1/8" thick. Any smaller and it didn't hold very well.

After much testing, we found that a N42 3/4" x 3/4" x 1/8" magnet worked best. Strong enough to "snap" to the surface, but not so strong that it was hard to get off. The K&J part number is BCC2. We only needed 2 magnets.

## Step 3: Test It Out!

Once you've sewed the magnets in place, test it out to see what surfaces you can stick your drink to! We tested it on pretty much every steel surface we could find...the fridge, a car, toolbox, etc. It worked great on each one!

Check out the video to see the different magnets we tested and how well they worked.

## Step 4: Important Physics

We always like to include something technical behind our projects and this one is no different! While the concept is simple, one very important takeaway is the leverage force.

The distance between the two magnets provides leverage, preventing the can from tripping away from the surface. If the magnets are too close or if you only use one magnet, the can will tip away from the surface.

This is because the can's center of gravity is out away from the surface and wants to rotate free. If the strong friction from the bottom magnet is holding the can from slipping, the top magnet opposes the torque from the weight of the can. The greater the distance between the two magnets, the greater the torque the top magnet will provide.

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## Discussions

this is fun! not the most practical invention but still cool.