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WHY PIN PIERCES ?


     The force acting on unit area is called pressure.  Some times, we  want to know what is the pressure give by the atmosphere and it is easier to measure.  
     When we press on the head of the pin , we give force through the pin to its pointed end.  That is, we concentrate the force on very small area and there by increase the pressure.  Hence the pin easily pierces an object.  For the same reason, a knife cuts.
     There are machines which produces jet of water with so much pressure that even cut metals.  Pressure does work.  So it is also a source of energy.   

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