Download the files:
Cut-outs
Instructions

How do I make it?

1) Fold along all the long lines (you may need to score them with a pen first). The sheet should form a zig‐zag pattern.  
2) Squeezing the ridges together, cut along the lines that run across the folds.  
3) Turn over, carefully cut joining piece in half and secure with sticky tape.  
4) Place magnets in the gaps and tape into place. Arrange the metal balls as shown. Push the first ball (X) towards the magnet.  

Watch the videos:
Video 1
Video 2

How does it work?

It seems strange that when you roll a ball towards the first magnet, the ball all the way down the other end eventually flies off at a much faster speed than the first one! Thinking about it, the ball seems to gain energy for free. But we know that this can't be true - you don't get something for nothing - so where does the energy come from?

The initial configuration fo the accelerator looks like:

After the accelerator has been set off, it looks like:

The fact that the energy changes from ball to ball down the accelerator is just like in a Newton's Cradle - it is a transfter of momentum. The ball ont he left hits the magnet and it's momentum gets transferred throught to the ball on the far side, just like in billiards. But that doesn't explain why the final ball moves faster. The trick is that the second setup has a lower magnetic potential energy that the first. Some of the potential energy of the initial setup is converted into kinetic energy of the final ball, making it go faster. So overall, the system has the same total energy the whole time, but it is converted from one type to antoher.


Experiments to try

  • Try changing the initial configuration of metal balls. For example, try starting with just one ball next to each magnet. Does the accelerator still work? Why do you think this is?
  • Try changing the distance between the magnets (you can do this by creating another magnet gap just as when you made the accelerator). Does this affect how fast the final ball goes?
  • Why do you think a real article accelerator doesn't use magnets to accelerate the particles?