Broomstick Superpower
Word of the day: pulley
“Can you pull two grown-ups across the room all by yourself? Let's find out.”
Grab
- two broom handles or mop handles
- a rope about 4 m long
- a second grown-up (or tie one broom to a heavy table leg)
Grown-ups hold on gently and let go if hands get pinched between handles.
Do
- Two grown-ups each hold a broom handle, about a meter apart, and try to keep them apart.
- Tie the rope to one handle and pull it straight. Hard to move.
- Now wrap the rope back and forth around both handles 4 or 5 times. Give the kid the free end.
- They pull. The grown-ups slide together. Try with fewer wraps and more wraps.
The big moment
A four-year-old drags two grown-ups across the room.
Ask (guess first, then try)
- Did more wraps make it easier or harder?
- Who is pulling farther, you or the brooms?
What's going on (for you)
Each wrap of rope adds another strand pulling the brooms together, like a block-and-tackle pulley. Five wraps can multiply their pull several times (friction eats some of it). The price: they have to pull a lot of rope to move the brooms a little. Same trade as the lever.
If they want more
Hang a rope over a banister or a broom laid between two chairs and pull down to lift a bucket of toys up. A single pulley lets you pull down to lift up. The bucket weighs the same.