A pulley system in action.
Pulley systems use applied force and physics to move heavy objects with a minimum amount of leverage. A model pulley system makes an excellent science project, because you can see the science in action and pose a number of questions regarding force, leverage, and physics.
Model elevator
Build a basic elevator system using a small cardboard box, several spindles, thread, a sheet of plywood or strong cardboard, and a nail as a counter weight. Use the cardboard or plywood as your backing to attach four nails or tacs at the top, at equal lengths apart from each other. Place the spindles on the nails so they can rotate and spin. Attach two spindles at the bottom in a similar fashion, one in the center, and one in the left corner. Attach two lines of thread to the top of your cardboard box, which should rest in the center. Tie the lines together an inch above the box, one thread should attach to the left two spindles, then move downward to the bottom left spindle, wrapping around the center bottom spindle and upwards to attach the to bottom of the box. The remaining thread on the top of the box should wrap around two spindles on the right side, then attach a nail to the thread as a counterweight, you now have a working elevator model.
Block-and-tackle pulley system
You can illustrate how pulleys work by building a basic block and tackle pulley system to lift a heavy crate. Attach three spinning wheel pulleys to the ceiling, 6 to 8 inches apart. Attach two identical spinning wheel pulleys on top of the box, facing upwards toward the ceiling, 6 to 8 inches apart aligned with the ceiling pulleys. Weave your rope through the top spindle on the ceiling, then under the first spindle on the crate and back over the second ceiling spindle. Then continue to weave the rope under the second crate spindle, over the final ceiling spindle. Tie the end of the rope to the top or side of the box.
You now have a working pulley system that can lift a very heavy box with only a small amount of force. You can experiment with the weight of the box or the number of people pulling on the box to find out how much force is required and how much energy the pulley actually saves you.
Egyptian pulley replica
Construct a pulley system modeled after the one ancient Egyptians used to haul the giant pieces of stone required to construct the pyramids. Place a square piece of cardboard over six to 10 identical rounded crafting sticks. Place a heavy piece of stone on top and tie some string around it. Pull on the string and stone will start to move forward, aided by the crafting sticks underneath it.
When one of crafting logs rolls out from behind the strip of cardboard, place it in front of the contraption. When this happened during the construction of the pyramids, workers would hoist the logs up and run them to the front of the contraption again.
Tags: pulley system, ceiling inches, ceiling inches apart, ceiling spindle, crafting sticks, front contraption