Homemade Pulley System

Build your own pulley system to discover how simple machines make lifting heavy objects easier. You'll learn about mechanical advantage and how redirecting force can help you move loads with less effort.

Tools

• pencil (1)

Materials

• empty thread spools (plastic or wood, 2)
• strong nylon string or twine (10 feet)
• small plastic bucket or basket (1)
• small weights or pebbles (approx. 1 lb)
• strong adhesive tape or zip ties (4)
• cardboard scrap (12x12 inch piece, 1)

Safety

• Adult supervision required for sharp objects.
• Do not wrap string around neck or limbs.

Steps

1. Prepare your fixed pulley by taping or zip-tying one thread spool to a sturdy overhead support (like a table edge, a door frame, or a cardboard beam attached to a wall) so that the spool can rotate freely.
2. Cut a length of string (about 8 feet) and tie one end securely to the handle of your small bucket or basket.
3. Thread the string over the top of the first (fixed) spool. This creates a simple pulley that allows you to pull down to lift the object up.
4. To create a system with mechanical advantage, take the second spool and tie the string to the center of the spool's axle or create a loop that holds the spool.
5. Position the second spool (the movable pulley) underneath the bucket. The string should go up from the bucket, over the fixed spool, down through the movable spool, and then back up to be anchored to the ceiling or support beam.
6. Place your weights or pebbles into the bucket.
7. Pull the free end of the string. Notice how the bucket rises. Because the load is now supported by two segments of rope, you only need to apply half the force to lift the weight.
8. Experiment by adding more spools to see if you can make the heavy object feel even lighter!