Elephant & Mouse Riddle

Hello there,

I am a Physics teacher who works at the Schwartz/Reisman Science Education Center, and as part of my job I helped develop a demonstration concerning circular motion.

The riddle goes like this: How can a light weight (mouse) lift a heavy weight (elephant), while both are tethered?

The answer is in the video below, meanwhile - let's see how the riddle is built:

Tools:

3D printer

File

Ratchet

Scissors

Sewing needle & thread

Craft knife

Needle-nose pliers

Supplies:

3D filament (I recommend PLA)
Large Nut & Bolt

1 meter Twine

Toy mouse

1/2" diameter PVC pipe, roughly 10 cm long

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Step 1: Printing the Elephant

I began with the large weight - making the elephant. I found a 3D model on Thingiverse here, and using tinkercad

added a screw-hole that was 5 cm long and 1 cm wide, roughly the size of my bolt.

I then printed the elephant with supports, the supports are important for overhanging regions.

Unfortunately, there are supports also in the hole, so I used a needle-nose pliers to remove them.


Step 2: Operation!

I needed a mouse, so I went to a local pet store. Not to buy a live one - but to buy a toy mouse intended for house cats.

I then made a vertical incision in the abdomen, and tied the twine to the nut.

I put the nut inside the mouse and sewed the incision using the needle and thread.

Step 3: Putting It All Together

It's best to smooth the edges of the pipe using the file in advance.

Next, thread the twine through the pipe and tie the other end to the bolt.

After that, screw the bolt to the back of the elephant using the ratchet - and you're done!

Step 4: Demonstration Time!

As you can see in the video, the light mouse is able to lift the heavy elephant thanks to circular motion. The radial acceleration causes a net force on the elephant, causing it to rise.

Originally, I thought to 3D print the mouse, put slinging hard plastic is a bit dangerous...

I hope you enjoyed this Instructable and please vote for me in the Classroom Science Contest.

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