Resistance - paper helicopters - air resistance against propellers slows and spins the paper slowly to the ground.
Pollution in our water - everyday normal items can pollute the waterways. The experiment showed how polluted and murky water became as each item was added to clean water.
Centrifugal force (eventually) Found these projects at a backyard sale this summer and some of the wires became detached and didn't work, but these boys fixed every one of them and they all work! :)
Machines and Gadgets - incline planes, levers, wedges, pulleys, screw and wheel and axle. This project demonstrated the wheel and axle type of machine. It is not just for tires and wheels.