Explanation of some everyday observation on the basis of pressure.....

                             Pressure
Pressure is the force acting perpendicularly on a unit area of the object. The effect of a force depends on the area of the object on which it acts. Please note that the weight of a body is also a force. And it is always act in the downward direction.
The pressure depends on two factors : 
1. Force applied, and 
2. Area over which force acts.
      The same force can produces different pressures depending on the area over which it acts. For example, when a force acts over a large area of an object, it produces a small pressure. But if the same force acts over a small area of the object, it produces a large pressure.
        Pressure  = Force
                              Area
The SI unit of measuring pressure is 'newtons per square metre' which is also called Pascal (Pa).
 Explanation of some everyday observations on the basis of pressure ...
We have just studied that 'pressure is the force per unit area'. This definition of pressure can be used to explain many observation of our daily life. An important point to be kept in mind in this regard is that the same force produces less pressure if it acts on a large area
but it can produce high pressure if it acts on a small area.
1. Why School bags have widstraps.  A school bag has a wide strap so that the weight of books may spread over a large area of child's shoulder producing less pressure (and hence less pain)
2. Why a Sharp Knife Cuts Better than a Blunt Knife. A sharp knife has a very thin edge to its blade. A sharp knife cuts object (like vegetables) better because due to its very thin edge, the force of our hand and falls over a very small area of the object producing a large pressure. And  this large pressure cuts the objects easily. On the other hand, a blunt knife has a thicker edge. A blunt Knife doesn't cut an object easily because due to its thicker edge,  the force of our hand falls over a large area of the object and produces lesser pressure. This lesser pressure cuts the object with difficulty.
3. The tractors have broad Tyres so that there is less pressure on the ground and the tyres do not sink into comparatively soft ground in the fields. The wide tyres of this tractor spread the weight of tractor and trolley over a large area of ground producing Lesser pressure on ground so that it can travel over soft or muddy ground without sinking in it. 

I am Saheb Sarkar from purnea .

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