You may not be able to lift a large rock on your own, but a lever and fulcrum will help you move the rock without exerting much energy or effort. The fulcrum is the part of the machine where the lever pivots or balances. For example, on a teeter-totter, the fulcrum is the center and the lever. Go out into the playground or a park and experiment lifting heavy objects with levers of different lengths, with the fulcrum placed at different positions, and record the results. Determine if there is a correlation between the length of the lever and the position of the fulcrum and the age or size of the person.
Pulleys, comprised of a rope and a wheel with a groove in it, help people lift heavy objects by bearing some of the weight. Although just one pulley helps people lift objects, the more pulleys you use, the easier it will be to lift things. Pulleys don't take up a lot of room, aren't weakened with length of the rope and can easily change directions.
Set up a project where students use pulleys to lift a chest of ice. Show students how to use a single pulley. Let each student in the class lift the chest off the ground with the single pulley. Then install a second pulley, and allow students to compare the differences. According to the Mini Science website two pulleys reduce lifting force by 50 percent, and three pulleys reduce lifting force by 75 percent. Although you may not be able to notice the percentage of lifting force saved, you can add more weight to the ice chest as you go along.
Wheels also help people move things easier. For example, if your friend was sitting in a box, it would be difficult to push or pull the box across the ground, but a friend in a wagon with wheels is easy to move. Let students experiment with small cars with and without wheels. Gently push a car with wheels across the ground, and then push a similar sized car without the wheels. Ask students which car traveled farther. Do the same push test down a ramp to see which car traveled farther. Point out that wheels reduce friction on the ground and allow objects to move faster. Experiment with the number of wheels on objects to see if the number of wheels on an object allows it to travel faster or easier.
Inclined planes, also known as ramps, help people move things easier from one level to another. Test the efficiency of ramps at varying angles to help determine what makes moving things easier. Experiment moving things both up and down the inclined plane at various angles and working with wheels on the ramps too. Test inclined planes of varying surfaces. For example, lay rough sandpaper on an inclined plane and see how far the car travels. Then add slippery soap to an inclined plane to see if that reduces friction and allows the car to travel even farther.