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Science project idea

Cardboard marble roller coaster: height, speed and loops

A marble released from high up gains speed as it rolls down, trading height (potential energy) for speed (kinetic energy). It can climb a hill or go round a loop only if it started higher than the top of that hill or loop, and friction steals a little energy all the way.

Make it yourself9 numbered steps, the materials and the science, all free.Go to the stepsGet a ready-made kitReady-made models, kits and spare parts in the store under Best Out of Waste.Browse Best Out of WasteAsk on WhatsAppAsk the head office whether a model or kit for this idea is available.Send a message

What it shows

A marble released from high up gains speed as it rolls down, trading height (potential energy) for speed (kinetic energy). It can climb a hill or go round a loop only if it started higher than the top of that hill or loop, and friction steals a little energy all the way.

The science

A marble held high on the track has gravitational potential energy because of its height. As it rolls down, that energy turns into kinetic energy and the marble speeds up; as it climbs, the kinetic energy turns back into potential energy and it slows down. The marble can never reach a point higher than where it started, and because friction and air resistance turn a little energy into heat at every moment, it actually falls short of that height. To go round a loop the marble needs extra speed at the top so that it keeps pressing on the track, which means the start must be noticeably higher than the loop.

Materials

Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.

  • Long strips of cardboard from old cartons, folded into U-shaped channels (free)
  • A large cardboard box or a wall to tape the track to
  • Marbles
  • Masking tape and a stapler
  • A ruler or measuring tape
  • Paper cups as stands

Safety

For this project: An adult must cut the cardboard with a knife; marbles are a choking hazard for young children.

Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.

All the safety rules

Step by step

9 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.

  1. Fold each cardboard strip along two lines to make a channel about 3 cm wide with raised sides.

  2. Tape the first strip high on the box, sloping down steeply, and test that a marble rolls smoothly along it.

  3. Join strips end to end with tape on the underside so the joins do not bump the marble.

  4. Add a hill: curve a strip up and down and find the highest hill the marble can cross from your starting height.

  5. Lower the starting point and show that the marble now stops before the top of the hill.

  6. Bend a strip into a loop about 20 cm across, tape it firmly, and find the lowest starting height that gets the marble round.

  7. Measure the start height and the loop height and note that the start must be clearly higher than the loop top.

  8. Add a long gentle run-out at the end and measure how far the marble travels before stopping; this shows friction.

  9. Draw a diagram of the track labelling where potential energy is greatest and where speed is greatest.

What you should see

A working track on which the marble crosses hills and loops a loop when released high enough, and fails when released too low. The required start height for the loop is clearly above the loop top.

Viva questions

A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.

1Where does the marble have the most potential energy?

At the highest point of the track, usually the start.

2Where is it moving fastest?

At the lowest point, where most of the potential energy has become kinetic energy.

3Why can the marble not climb back to its starting height?

Friction and air resistance turn some of its energy into heat along the way.

4Why must the start be higher than the loop?

The marble needs extra speed at the top of the loop to keep pressing on the track and not fall off.

Free ebook: Viva Questions for Science Projects

Take it further

Time the marble over a measured straight section with a phone and work out its speed for different starting heights.

Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.

Free ebooks for this project

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