Things do not stop by themselves
A ball does not run out of go. It rolls until something stops it.
Step 1: Something to Notice
Watch first. The explanation comes later.
Slide a toy car on a carpet and it stops almost at once. Slide the very same car on smooth ice and it keeps going and going.
Why does the same car stop quickly on one floor and not on the other?
Step 2: Find Out
Keep the push the same. Change only the floor.
Step 1 — Predict
The same push on two different floors. Which one lets the ball go further?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
Rough floors
Carpet is rough. It drags on the ball, so the ball stops quickly.
Smooth floors
Ice is smooth. Almost nothing drags, so the ball slides and slides.
Keeping it fair
We changed the floor and nothing else. That is how we know it was the floor.
Step 4: A Common Mistake
Lots of people think
“Things stop by themselves when they get tired.”
Step 5: Why Ice Rinks Are Slippery
The same idea somewhere new.
Skaters glide a long way on ice because it is so smooth. On grass they would stop straight away.
Step 6: Think It Through
Practice makes it stick.
The Toy Car
Problem 1 of 1
Sam pushes his car on the rug and then on the kitchen floor, the same way both times. Where does it go further?
What Stops It?
1 of 3
A ball rolls across carpet and stops. What stopped it?
2 of 3
Which floor lets a ball roll the furthest?
3 of 3
Put each picture in the right box.
Tap something to move it.
- Empty
- Empty
Step 7: Quick Check
Show what you know.
Question 1 of 1
Why does a rolling ball stop?
What You Found Out
- Things do not stop on their own. Something stops them.
- A rough floor stops a ball quickly.
- A smooth floor lets it keep going.
For the grown-up
Stopping needs a push too — Catching a ball is a push against it. Brakes on a bike push on the wheel. Nothing stops on its own — something has to push back.
Rubbing slows things down — A ball rolling on grass stops faster than one rolling on a smooth floor. The rough grass rubs against it. Ice is very smooth, so things slide a long way before stopping.