Marble Run – Build It, Drop It, Watch Gravity Work

What Is a Marble Run?

A marble run is a track that carries a marble from the top to the bottom. Real marble runs are built from wooden blocks, plastic tubes, cardboard or even paper towel rolls taped to a wall. This one is built on the screen. Each part does one simple job: a ramp lets the marble roll downhill, a curved ramp turns a fall into a sideways roll, a bouncy pad throws the marble back up, a wall stops it, a funnel gathers it into one place, a peg knocks it to one side, a see-saw tips under the marble’s weight and a spinner turns when the marble pushes it, or turns on its own when its motor is on. Put the parts together in the right order and the marble lands in the cup.

The marbles move by the same rules as real ones. They fall faster and faster, they roll down slopes, they bounce less off a wooden ramp than off a springy pad, and they knock into each other when several are dropped together. That makes the page a good way to explore forces and motion before, during or after a science lesson, and it is fun on its own.

Gravity, Slopes and Speed

Gravity is the pull of the Earth. It pulls the marble straight down all the time, whether it is falling, rolling or sitting in the cup. When nothing is underneath, the marble falls and gets faster every moment: drop a marble on the empty board and watch how the gap between where it is and where it was grows as it falls.

On a slope, the ramp holds the marble up, so only part of the pull of gravity is left to move it, and that part points along the ramp. The marble rolls downhill and speeds up. On a gentle slope it speeds up slowly; on a steep slope it speeds up quickly. Children can test this by turning a ramp a little at a time and dropping the marble again. Ask them to predict first: “Will it go further or less far if the ramp is steeper?”

When the marble leaves the end of a ramp it keeps moving forwards while gravity pulls it down, so it flies in a curve. A faster marble flies further before it lands. This is why the position of the cup matters so much in the challenges: the same ramp at a different angle can make the marble land in the cup or miss it.

Bounce, Friction and Energy

A marble that has rolled down a long ramp has a lot of energy of movement. Where does it come from? From height. At the top of the board the marble has energy stored because it is high up; as it falls or rolls down, that stored energy turns into speed. A marble can never bounce higher than where it started, because there is no extra energy to lift it.

When the marble hits something, some of its energy is lost. A wooden ramp or a wall keeps only a little of the bounce, so the marble soon settles and rolls. The bouncy pad is springy: it keeps most of the energy and sends the marble back up, almost as high as it came from. Rubbing against the ramp, called friction, takes a little energy too, so a marble rolling on a flat shelf slowly comes to a stop. Older children can explain each challenge in these words: “The marble gets its energy from falling, the ramp turns the fall into a roll, and the bouncy pad sends the energy back upwards.”

See-saws and Spinners: Levers and Wheels

The see-saw is a lever: a plank that turns on a pivot in the middle. When the marble lands on one side, its weight pushes that side down and the other side up. The further from the pivot the marble lands, the harder it turns the plank, which is why a small child at the very end of a playground see-saw can lift a bigger one sitting near the middle. Once the plank has tipped, the marble rolls off the low side, so the see-saw works like a switch that sends the marble one way or the other depending on where it lands.

The spinner is a wheel with arms. A marble that hits an arm pushes it round, and the moving arm pushes the marble on, often in a new direction; then the wheel slowly runs down, because a little energy is lost each turn. Choose a spinner and tap Motor to make it turn by itself, like a water wheel or a conveyor, and it can lift or carry a marble that has stopped. Tap Arms to give it two, three or four arms.

Think Like an Engineer

Engineers solve problems with a cycle that children can learn early: plan, build, test, improve. The challenges are built around it.

1. Plan. Look at where the marble starts and where the cup is. What is in the way? Which parts are in the box? Point with a finger along the route you think will work.
2. Build. Add the parts and drag them into place. Turn them to the angle you planned.
3. Test. Drop the marble and watch carefully. Where exactly did it go wrong? Did it fall short, overshoot or bounce out?
4. Improve. Change one thing at a time, then test again. Moving a ramp a little or turning it one step is usually better than starting over.

Every challenge can be solved in more than one way. Three stars go to a run that uses the smallest number of parts, which encourages children to look for a cleverer route rather than adding more and more parts. Talking about failed runs is part of the fun: a marble that misses teaches something every time.

How to Use This Page

1. Choose Challenges or Free build. Challenges have a cup to reach and a box of parts; Free build gives you every part and lets you move the marble dropper and the cup.
2. Add a part by tapping it in the list. It appears on the board, ready to drag.
3. Turn a part with the ↺ and ↻ buttons or by double-tapping it. Each tap turns it by 15 degrees. A chosen spinner also has Arms and Motor buttons.
4. Drop a marble with ▶ Drop, or drop five at once and watch them knock into each other.
5. Remove a part by choosing it and tapping Remove part, and clear the marbles to try again.
6. Save a picture of a run you are proud of. Your free build is kept on this device, so it is still there next time.

Ideas by Age

• K2 to P1: drop marbles on the empty board and on one ramp. Talk about up, down, fast and slow. Try the first three challenges together, with an adult doing the dragging if fingers get tired.
• P2 to P3: predict before every drop. Will the marble reach the cup? Which way will it bounce off the peg? Count how many parts a run needs and try to beat it.
• P4 to P6: explain each challenge with the words gravity, slope, friction and energy. Change only one thing between tests, as in a fair test, and record what happened. Design a run in Free build that uses every kind of part and still ends in the cup.

Ideas for Parents and Teachers

• Build a real one too. Cardboard tubes taped to a door, a shoebox lid and a marble make a great follow-up. Compare: what works on the screen that is harder in real life?
• Make it a fair test. In Free build, put one ramp at three different angles, drop a marble each time and mark how far it lands. Only the angle changes; everything else stays the same.
• Swap challenges. One child builds a run in Free build and saves a picture; another tries to build the same run from the picture.
• Use the words. Pause a run and ask what is happening: falling, rolling, bouncing, stopping. Naming the movement is the first step to explaining it.

Nothing to Install, Nothing Uploaded

The marble run runs entirely in your browser on any phone, tablet or computer, with no account and no download. Your free build and the stars you earn are kept only in your own browser; nothing is sent to us, and a saved picture goes straight to your own device.