Rough and Smooth: Why Things Slow Down
- Physics
- Ages 6–8 · Grades 1–2
- Hands-on experiment
What you’ll find out
- Rubbing between surfaces, called friction, slows moving things down.
- Rough surfaces make more friction than smooth ones.
- Friction can be useful, because it stops us slipping.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
Why things stop
Slide a toy across a smooth floor and it goes a long way. Slide it across a rug with the same push and it stops quickly. The rug is rough, so it rubs against the toy more. That rubbing is called friction, and it slows moving things down. Ice is very smooth, with very little friction, so things slide a long way on it.
Friction helps us too
Friction can be very useful. It is what lets you walk without slipping. Shoes have bumpy, rubbery soles that grip the ground. In socks on a smooth floor you can slide and fall. In winter, people spread sand or grit on icy paths. The rough sand adds friction, so feet and car tyres grip instead of sliding.
Curriculum links: NGSS K-PS2-1 · NGSS K-PS2-2