Science Projects And Inventions



  • A ruler


It is well known fact that if you rest a ruler one on each end of your extended forefingers, and if you move them towards each other they will perforce meet at the centre of the ruler. The explanation is simple. Should one finger travel ahead of the other, the weight on that particular finger increases.

Therefore, it raises the friction between the ruler and the finger. This in turn lowers the friction on the other finger allowing it to travel ahead. Now the question is: In a situation where both fingers are at the centre of the ruler, what is likely to happen should you move them back to the ends of the ruler. Trying guessing the answer before you  try the experiment. You are likely to be surprised.


 When one finger begins to move, its friction with the ruler decreases. The more it gets ahead, the less the friction. What you will find is that the first finger that begins to move will reach all the way to the end while the second one will remain static at the centre of the ruler.


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