The Magic Fork
Word of the day: lever
“I bet you can lift this big heavy book with ONE finger. Want to see how?”
Grab
- ruler or paint stirrer
- thick marker or round pencil (the pivot)
- a heavy-ish book
- a few toy cars or blocks
Do
- Lay the marker on the table. Put the ruler across it like a seesaw. That marker is the pivot.
- Put the book on one end. Push down on the other end with one finger.
- Slide the pivot close to the book. Push again. Then slide it far from the book and push again.
- Swap: stack the toy cars on one end and see how far out a single car on the other end has to go to lift them.
The big moment
Let them try with the pivot near their hand first. Then move it. Same finger, suddenly easy.
Ask (guess first, then try)
- Where should the pivot go to make it easy?
- Which end moves farther, your end or the book's end?
What's going on (for you)
A lever trades distance for force. Long arm on your side, short arm under the load: you push gently but a long way, the load rises a short way with a big force. Same rule as using a fork to pry up a cutting board.
If they want more
Hunt for levers around the house: scissors, a bottle opener, a door handle, a seesaw, your own arm at the elbow.
Look it up
Wikipedia: Lever PhET simulation