The Draughts Trick

What you need

  • Some low quality draughts (ones which do not lock together when stacked, but are solid and have a bit of weight).

What you do

  1. Stack a black draught on top of a white one, then pile three more white draughts on top.
  2. Roll a draught at the stack. You will need to create backspin by squeezing the draught down with your finger so it fires out forward.
  3. Keep practising until the black draught is hit by the rolling draught and flicks out of the pile, leaving the others undisturbed.

What's going on?

Newton's 1st law explains why this is possible. The draughts all have a certain inertia while sitting on the table - they won't move unless they are acted on by a force. The rolling draught provides that force to only one of the draught pieces - the black one in the middle. The only force the other draughts feel is a little friction between the pieces - pulling them out in the same direction as the black draught. If the pieces do not lock together this friction will be low, allowing the black to slide out without much resistance. Any friction that they do feel will be made less effective if the draughts are reasonably heavy (Newton's 2nd law tells us the more massive an object is the less it will move when acted on by a force).

The reason the rolling draught is given some backspin is to prevent it carrying on after the collision and bringing down the whole stack. It is hoped that at collision this 'rolling' draught is brought to a stop, its backspin then carries it away from the stack in a similar way that backspin is used in snooker to position the white cue ball.