WHY WOODEN CORK FOR WINE BOTTLE?

Take a piece of rubber. Stretch it. It will elongate lengthwise but will contract breadth wise. Now compress it. It gets shortened length wise. But stretches breadth-wise. Rubber is said to have 'positive poisson's ratio'.
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Suppose, we use rubber cork with wine bottle. When we press it into the mouth of the bottle, it will expand sideways. It may not go inside. It may even break the neck of the bottle. The wooden cork has 'zero poison's ratio'. That means, forces causes no effect in it. Hence, we can easily close and open the bottle with it.

There are some materials with negative poison's ratio. They are called "auxetic material". They have special structures as shown in the figure. Hence, their behavior is exactly opposite to that of the rubber. When stretched, they elongate on both sides. When compressed, they are shortened on both sides (length, breadth). Hence, they withstand strong force and pressure. They cannot be easily fractured.

' Auxetics' are used in the sports helmets (bike races).
Also used in body armor, packing material, knee and elbow pads.
Tendons in the body are natural auxetics.
In sport shoes, running track etc.

POISON'S RATIO -SIMPLIFIED

Strain = change in length/original length
Poison's ratio = breadth wise strain/lengthwise strain

It is normally in the range -1 to 0.5. Mostly poison's ratio is positive. That is, if the material is enlarged in one dimension, it will be shrieked in other two dimensions.. The materials of negative poison's ratio' is very rare. These are meta-materials belonging to the future.

Poison's ratio is mainly used by engineers to find"how much pressure a material can withstand before it collapses".
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THE EARTH, A SUPER ORGANISM

JOIN MY COURSE: "Become a programmer in a day with python" A man called 'love lock' (what a name) proposed a theory called Gaia theory, named after Greek Goddess. It says, "Earth is a self-regulating organism like a human being. The organic life in it interacts with in-organic matter and maintains atmosphere, temperature and environment". Hence the earth is still suitable for the life to thrive. Imagine, in a particular place, there are lot of flowers. Some flowers are white and some are darkly coloured. We know, white reflects light and heat while dark absorbs the same. White flowers can thrive in hot climate. But dark flowers requires cold climate. The absorption and reflection balances and the environment reaches average, warm temperature at which both the flowers can co-exist. This is the essence of "Gaia" theory. On our earth, the oxygen constitute 20% of the atmosphere. The oxygen level is always mai

THE PARABOLA

A jet of water shooting from a hose pipe will follow a parabolic path. What is the so special about parabola. Y= x^2 Draw a graph for the above equation. It will result in a parabola. This parabola is also called unit parabola. Any equation involving square will yield a parabola. Example: Y = 2x^2 +3x+3 (also called quadratic equation) X= 2 and -2, both satisfies the equation 4 = X^2. Parabolic equations always have two solutions. Any motion taking place freely under gravity follows parabolic path. Examples: An object dropped from a moving train, A bomb dropped from flying plane, A ball kicked upwards. If a beam of light rays fall on the parabolic shaped mirror, they will be reflected and brought to focus on a point. This fact is made use of in Dish Antenna, Telescope mirrors, etc. Inverted parabola shape is used in the construction of buildings and bridges. Because the shape is able to bear more weight. A plane

DISORDER IS THE "ORDER OF THE DAY"

Imagine a balloon full of air. The air molecules are moving randomly inside the balloon. Let us pierce the balloon with a pin. The air rushes out. Why should not the air molecules stay inside the balloon safely and ignore the little hole? That is not the way the world works. The molecules always "want to occupy as many states as possible". Hence the air goes out in the open to occupy more volume. The things always goes into disorder (entropy) and the disorder increases with time. The above statement is what we call "second law of thermodynamics". Consider a cup of coffee on the table. Suppose the heat from entire room flows to your cup of coffee, the coffee will boil and the rest of the room will freeze. Freezing means bringing things to order and arrangement. It violates the second law. Hence it will never happen. Hence heat must flow from high temperature to low temperature and not the other way. The air molecules in y

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