Slippy and Grippy
Word of the day: friction
“Why can you slide in socks on the floor but not on the rug?”
Grab
- the ramp from Ramp Racers
- a toy car or a block
- three ramp coverings: a towel, foil or wax paper, sandpaper or a bath mat
Do
- Slide the block down the bare ramp. Mark where it stops.
- Cover the ramp with the towel and try again.
- Try the foil, then the grippy mat. Line the marks up: slippiest to grippiest.
- Rub hands together fast. They get warm. That's friction too.
The big moment
The grippy mat stops the block dead.
Ask (guess first, then try)
- Which was slippiest?
- Why do shoes have bumpy bottoms?
What's going on (for you)
Friction is the rubbing force between surfaces that slows things down. Rough surfaces catch on each other; smooth ones slide. The rubbing turns motion into heat, which is why hands warm up.
If they want more
Socks vs shoes on the kitchen floor (carefully). Ice is slippery because a thin wet layer acts like a slide.
Look it up
Wikipedia: Friction PhET simulation