Build your own pulley system to discover how simple machines make lifting heavy objects much easier. You will learn about mechanical advantage and how redirecting force helps you move loads with less effort!

Tools

• scissors
• ruler
• permanent marker
• wooden skewers (2)

Materials

• empty toilet paper rolls (2)
• strong twine or nylon string (10 feet)
• cardboard scraps (2 pieces, 4x4 inches)
• plastic bottle caps (2)
• tape (1 roll)
• small basket or plastic cup (1)
• small weights like coins or pebbles (10-20 items)

Safety

• Adult supervision required when cutting cardboard and skewers with scissors.
• Be careful with the sharp ends of wooden skewers.
• Adult supervision required for sharp objects.
• Do not wrap string around neck or limbs.

Steps

1. Create the pulley wheels by taking the two plastic bottle caps and poking a hole exactly in the center of each using a skewer or scissors.
2. Cut two pieces of cardboard (4x4 inches) and cut a circular hole in the center of each that is slightly larger than the diameter of the toilet paper roll.
3. Slide a toilet paper roll into the cardboard hole and tape it securely to create a sturdy 'spool' shape.
4. Push a wooden skewer through the center of the toilet paper roll and attach the bottle caps to the ends of the skewer to keep the roll from sliding off.
5. Repeat the process to create a second identical pulley wheel.
6. Fix the first pulley to a stable point (like a door handle or a sturdy table edge) by tying the skewer or the cardboard support to the object using a piece of twine.
7. Tie one end of the 10-foot string to the handle of your small basket or plastic cup.
8. Loop the string over the first (fixed) pulley.
9. To create a 'movable pulley' for extra power, tie the other end of the string to the fixed support, then loop the string under the second pulley wheel, and finally bring the string back up and over the first pulley.
10. Place your weights (coins or pebbles) into the basket.
11. Pull down on the free end of the string and observe how the basket rises. Notice how it feels much lighter to lift than if you pulled the basket straight up!