Why do some floors let you slide and some grab your feet?
Some floors let you whoosh and slide… and some floors grab your feet and hold you still. A smooth, shiny floor feels slippy. A bumpy, fuzzy floor feels grippy. Now look — a little penguin is sitting at the top of a smooth, shiny hill. What will the penguin do? Ready to guess… will it slide down, or stay put?
After you watchWhy do some floors let you slide and some grab your feet?
The short answer
Smooth floors are slippery and bumpy floors are grippy. A smooth, shiny floor like ice has almost nothing to grab your feet, so you slide. A bumpy, rough floor like a rug or a sidewalk has tiny edges that grab and hold, so you stay put. How slippery something is depends on how smooth or bumpy the two things touching are.
Try this next
- What happens if you sit the penguin on the BUMPY hill instead? Picture the same penguin on the fuzzy bumpy hill, guess if it slides or stays, then look at the bumpy-hill picture and see.
- What if you find a smooth floor at home and a bumpy one? Slide a sock across a shiny floor, then across a rug, and feel which one lets you slide and which one grabs.
The whole story
How it works
When two things touch, the bumps on each one bump into each other and grab. A bumpy floor has lots of little edges, so it grabs your feet hard and holds you still. A smooth floor like ice has almost no edges to grab, so there is nothing to stop you and you slide right along. Grown-ups call that grabbing grip 'friction.'
What people get wrong
Little kids often think ice is slippery because it is cold, or because it is wet. But the real reason is that ice is very SMOOTH. A smooth floor has almost nothing to grab your feet, so you slide — and a bumpy floor grabs and holds even when it is cold.
The catch
Grip is a helper and a bother at the same time. A grippy bumpy floor keeps you safe so you do not slip and fall — but it is hard to slide a sled or a heavy box across it. A slippy smooth floor is super fun for sliding and gliding — but it is scary when you want to stop and your feet just keep going. So we pick bumpy or smooth to fit the job.
Questions kids ask
Why is ice so slippery?
Because ice is very smooth. A smooth floor has almost no little edges to grab your feet, so there is nothing to stop you and you slide.
Why do my shoes grip the sidewalk?
The sidewalk and your rubber soles are both bumpy. Their tiny bumps grab onto each other and hold tight, so you stay put instead of sliding.
Does a wet floor make you slip?
Yes! A puddle of water makes a floor extra smooth and slippy, because the water slides easily and keeps the bumps from grabbing. That is why a wet floor is so slippery.
Talk about it
- Before we look: a penguin on a smooth shiny hill — do you think it slides or stays? Why?
- Can you find me one slippy floor and one grippy floor in our house?
- What could we add to a slippy floor to help our feet grab it?
Keep going
What else makes you wonder?
- What floors at home are slippy, and what floors grab your feet?
- Why do you think a wet floor gets even more slippery than a dry one?
- Could you make a slippy floor turn grippy by sprinkling something bumpy on it?