Rolling means moving along a surface by revolving, or turning over and over, and without sliding. When a cylinder rolls, it tends to roll in a straight line. But if one end is wider than the other, it will go around in a circle. I used to call this technique the “Differential Compass”, but now I just call it the “Rolling Cone”
There are many things that might be lying around your house that can act as a rolling cone. See what you can find.
The wider side travels further than the narrower side with each rotation of the cone. If both sides were the same size, it wouldn’t be a cone, and it would roll in a straight path. Try this with other objects, and observe how the path changes, as you change the cone.
All complicated machines are made from simpler parts. If you haven’t mastered this technique, or don’t yet understand it, break it down into smaller parts till you “get” each one, and then build up from there. Find or make a cone shape that will roll on a curve. Input force on one end, and the cone will output force at the end of its curved path. Place the cone on a surface slightly higher than the table, like a domino, which stores a bit of potential energy, and adds to the force of the rolling cone when that potential energy is converted to kinetic (movement) energy.