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Science progress affects our daily life and "to know" means you are going to chose right, because it allows you to form your own opinion on scientific everyday issues. On the other hand, having an elegant and harmonious vision of the world where we live in leads to a feeling of intellectual satisfaction.
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Wednesday, December 28, 2011

Counterintuitive Demonstration- Ciment rice

Today we are going to see a weird demonstration. Not a weird "weird" demonstration, but let's say it defies logic, with this experiment we want to show that, in order to think science, we need to clear our mind from some preconceived ideas. This is a real problem, often we do not place certain questions because we are sure of the answers, and this is bad science.

NOTE: This demonstration needs adult supervision.

What we need:
  • rice,
  • a plastic jar, we used a baby's bottle,
  • a knife,
  • resistant surface, like a kitchen counter,
  • patience and a broom.
How to:
  1. Fill the jar with rice;
  2. Plunge the knife "halfway" into the rice a few times; it's easier if you lean the jar 5 or 6º;
  3. Fill the jar again, repeat the process;
  4. With a fast and clean hit, jab the knife up to the hilt into the rice, be careful with your hands, an adult must supervise this step;
  5. Pull the knife straight up.
What happens?
The jar comes up with the knife.

The force of pressure can overcome the force of gravity.
The preliminary stabs made rice grains to settle in close to each other. Thousands of rice grains surrounded the knife when we plunged it halfway, after each stab, the grains got closer and closer.
In the last step we pulled the knife straight up into the settled in rice, the knife is sharp enough to be jabbed into this network of pressure, but at same time the rice settles back in from all sides to hold the knife in place.

Please Note:
It's normal if you have to repeat several times the steps above until you have success. Persistence is the key; you may try to change the knife or the container.

This demonstration can be an experiment, or a science fair project:
  1. Change the container, different volume, high...;
  2. Change the knife width, length, or material....;
  3. Change the rice; use other grains, sugar, salt, sesame seeds, sand...
Record the weights of the containers with and without rice, record the width / length of the knife and all the variables of your essay.

Et Voilá!


Connolly, Sean, "The book of totally irresponsible science", 2008

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