Build a marble run
You will build a low rolling route and time the ball from start to finish. A very flat route slows it, but may stop it before the finish.
- Build
- Expert
- About 25 minutes
Grown-up needed: yes for setup, nearby supervision and clearing spills or loose pieces
What you need
- Whole cardboard tubes
- Sticky tape
- A small ball chosen by a grown-up
- A low tray
- A timer
The rule
The marble must roll for 5 seconds.
How to do it
- Ask a grown-up to choose a ball and whole tubes that need no cutting.
- Arrange the tubes in a low descending route inside the tray.
- Tape each tube to its support without blocking the opening.
- Place the ball at the marked beginning of the route.
- Release it while a grown-up times the complete roll.
- Lower one slope slightly and repeat from the same start.
Why it works
Gravity supplies energy as the ball moves to a lower position. Some energy goes into forwards motion and some into rolling. Rubbing and bumps can slow the ball or stop it. A gentler slope may reduce its speed, but a section with no useful drop can leave too little motion for the next tube. Timing the whole route shows whether you made a slower successful journey or simply created a stopping place.
Make it harder
- Add one more whole tube.
- Keep the route length while reducing its total drop.
- Make a route lasting longer without any pauses or pushes.
Ask Taz
- Why does a steeper slope speed the ball up?
- Why does my ball stop at a tube join?
- Why can a flatter route fail even when it is longer?
For grown-ups
Stay with the small ball and keep it away from younger children. Build only low routes, without chairs to climb. Let your child distinguish a stopped ball from a slow continuous roll. Ask at dinner: “Which part took the longest, and how would you find out without changing the whole route?”
Taz is an AI and can be wrong, so stay close by. Read how safety works on Taz.
Show us yours
Film your hands and what you made, not your face or name. Ask a grown-up before posting anywhere else.
Questions parents ask
Do we need special equipment?
Use the household items listed above. Begin with a small attempt on a clear surface before trying any harder version. The listed time is an estimate, so leave room to rebuild or repeat without rushing.
What if the first attempt does not work?
Notice where the result first changed. Alter one feature, keep the rest similar and try again. An unsuccessful attempt can still give you a useful question.
Do we have to post the result?
No. You can show it to a grown-up at home. Online sharing is optional and needs the permissions in the privacy line above.
More to try
See all Taz Challenges, or look through the science labs. One place for every why. Ask for early access at aitaz.com
Try it in 3D: Rolling race.