Students could design various educational toys such as: a balance scale using levers to teach weight comparison and arithmetic, a catapult to demonstrate projectile motion and angles, a windmill to show energy conversion from wind to mechanical energy, a rubber band car to demonstrate potential and kinetic energy, a pulley system to show how force can be reduced when lifting weights, a gear system to demonstrate ratios and multiplication, or a simple circuit toy to teach about electricity. The toy should clearly demonstrate the chosen concept and be made from waste materials using simple machines.