Rotational Motion Apparatus

This is my take on a device designed by Steve Rea. This device ended up being produced and sold by [Arbor Scientific](http://www.arborsci.com/rotational-inertia-demonstrator). Arbor's Rotational Inertia Demonstrator works amazingly well and is very repeatable. I highly recommend it. The cost really is quite reasonable for such a well built device. However, I decided to design a 3d printable one because our current physics teacher doesn't have the funds to buy a class set.

String is wrapped around one of the pulleys with a [weight hanging from the string](https://youtu.be/57WHc0DdW9s). There are three different pulleys to provide different amounts of torque. With an extra set of hex nuts the washers can be positioned different distances from the center of rotation changing the moment of inertia. There are a lot of experiments that students can do to investigate rotational motion.

Diameters of the three pulleys:
- 24.5 mm
- 49 mm
- 73.5 mm

**Update**: I uploaded a new versio