# Rolley Poley

Two wheels connected by a shaft which is articulated are provided, along with an inclined plane and copious amounts of silly putty or similar.

• Children can place the putty in different locations on the toy.
• Adding it uniformly around the axis of rotation will change the speed at which it rolls, depending on how close the weight is to the center of rotation.
• Adding the putty in an off-center way will make the rolling of the toy irregular, and maybe even prevent it from continuing down the plane.
• Adding the putty to the outside of the wheel would allow the toy to 'jump' as it rolled.
• Adding weight to just one wheel would cause the toy to roll in an arc.
• etc. etc.
• In addition to such experiments, many children would likely take a more artistic route and use the putty to decorate the toy - the packaging should encourage either use. Creative thought and exploration are to be encouraged in any form.
• The toy demonstrates rotational inertia, gravity (and its vector nature,) and inertia. Use of the hinge would also demonstrate a sort of dynamic geometry which I don't know a formal name for, but is very difficult for adults to intuit.
• The wheels and axle need to be relatively light as compared to the putty (which is thankfully fairly dense,) so that adding mass has a notable effect, but the toy must be durable. A strong plastic, or even a thin metal construction would be good materials.
• Inspiration for this toy came from this video (a short excerpt from a 30-minute long rube goldberg machine) which demonstrates many interesting and unusual physical relationships. I noticed, when I first watched it, that I had the least intuition for the rotational elements - I'd actually interacted with very few in my life, and wondered how people might learn this sort of intuition. Later, working on cars I developed a little more, but I wanted to find a way that was more accessible to younger children.

Ethan Weil
Carnegie Mellon University
January 25, 2010