Why is momentum represented by p?


In physics, there is a quantity that represents the product of mass and velocity of an object. That quantity is called as momentum. The popular equation for momentum according to the Newton’s law is that P=MV. Here, P stands for momentum, M stands for mass and V stands for Velocity of an object. If we observe the symbols used for various other quantities in physics, mass, time, velocity, force and acceleration are represented by their first letters. In this context, we might think that probably momentum is represented by P’ as ‘m’ was already used for mass. If ‘m’ was not used for mass, probably it could have been used for momentum. These usages existed since few decades.

Before the Newton’s period, it was believed that an object moves when a force is applied to it continuously. Later, Newton discovered ‘momentum’ which showed that object moves continuously without any force applied to it. The capacity or characteristic feature of the object to move continuously was called as an impetus. Though Newton talked about momentum, he did not formulate the equation P=MV. This equation was formulated after some time. This study was later called as Newtonian mechanics. In the place of previous ‘impetus’, the name momentum was used by the people. Probably, ‘P’ was a convenient symbol as per its previous name and that might have led to the representation of momentum with ‘P’. The letter is written in bold as the quantity is a vector.

Some interpret the reason for keeping P as the symbol for momentum as the letter being derived from Latin word Petere which means ‘to go and seek’. This meaning is also related to the word ‘impetus’ which is the earlier term used for ‘momentum’. The word ‘impetus’ gives the meaning as to go and rush upon which was explained by the term Petere. Hence, momentum is represented by the letter P.

Author: Hari M

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2 Responses

  1. kymberly

    November 21, 2012 5:58 pm

    this was very interesting…can you explain the conservation of momentum for me? i really need all the help i can get. Thanks.

  2. NS

    January 8, 2013 4:28 pm

    The correct formula for momentum should not be written with capital letters. Capital letters represent other quantities. So, the correct formula is p=mv.

    Capital P is power or pressure, capital V is volume.


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