The Obedient Can
You will need: A round can with lid, nail, hammer, rubber bands, thread, nut and bolt.
Your knowledge of the force of gravity will enable you to construct a simple mechanical toy which will obediently return when you roll it away.
Begin by hammering two holes in the lid and two holes in the bottom of the can with a nail.
Cut a long rubber band (or several knotted together) and pass it through the four holes in figure-of-eight fashion. See diagram. Tie ends of the rubber band together again.
Now tie a small weight, such as a piece of lead or nut and bolt, to the center of the rubber band, where it crosses inside the can.
Replace the lid and roll the can away from you. The weight supplies a lowered center of gravity which winds up the rubber band. When the force you have used has been expended, the band will unwind and the can will slowly roll back to you.
The thicker the rubber band, the quicker the toy
Children learn best through doing
Before children can understand a thing, they need experience: seeing, touching, hearing, tasting, smelling; choosing, arranging, putting things together, taking things apart. Experimenting with real things.
Old-time school teaching used only words and the teachers thought children knew something if they could repeat it. Now we know better. To reach practical understanding we do not need to use many words with young children.
Children are clever. They learn a lot, without being taught. The greatest skill - to be able to talk, to communicate is learnt outside school. In the classroom it's the children who need to talk the most. Unfortunately it is the teacher who does most of the talking!