How do people move pianos and heavy furniture into tall buildings? It's easy if the thing fits inside an elevator or they can carry it up the stairs. If not, they might use a simple machine. Show your kids some pulley potential with this simple household exercise!
What You Do:
- Run a piece of sting about 1 foot (30 cm) long through the hole in the spool and tie the ends of the string together.
- Slide the spool and the string onto the broom handle. Rest the handle across the two chairs with the spool hanging between.
- Put one pail on the floor and tie the end of the piece of ribbon to its handle.
- Slide the other end of the ribbon over the spool and tie it to the handle of the other pail, which should dangle in the air.
- Add a few pennies to the hanging pail. What happens to the pail on the ground?
- Return the pail to the ground and add a handful of pennies or marbles. Pull the handle of the hanging pail toward the ground. What happens to the pail filled with weights?
As you added pennies to the hanging pail, it started to lift up the pail on the ground. A single fixed pulley lets you pull in one direction to move a thing in the other direction. This is handy: it means you don't have to climb up a flagpole to raise the flag. Instead, you can stand safely on the ground and pull on the rope as the flag rises to the top!
Reprinted with permission from "Mighty Machines," the book that teaches kids the basics about how things work-- from pulleys and levers to screws and wheels! By Shar Levine and Leslie Johnstone (Sterling Publishing Co., 2004).