Momentum
Law of conservation of Momentum


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MOMENTUM


Quantity of motion of a body is referred to as "MOMENTUM".  
Definition


Momentum of a moving body defined as :  
"the
product of mass and velocity of a body is called MOMENTUM."


Mathematically  
Momentum
= mass x velocity




It
is a vector quantity. Momentum is always directed in the direction of velocity. The unit of momentum is in S.I system kg .m/s or NS. Momentum depends upon mass and velocity of body. 

LAW
OF CONSERVATION OF MOMENTUM.


The law of conservation of momentum states that:  
"when
some bodies constituting an isolated system act upon
one another, the total momentum of the system remains constant." OR
"the
total momentum of an isolated system of interacting bodies remains constant."
OR "Total momentum of an isolated system before collision is always equal to total momentum after collision." 

Consider an isolated system of two bodies 'A' and 'B' as shown. The masses of bodies are ma and mb and  
MATHEMATICAL
REPRESENTATION


Consider two bodies of mass m_{1} and m_{2} moving initially with velocities u_{1} and u_{2}.  


Total momentum before collision = m_{1}u_{1} + m_{2}u_{2}  


Let after collision their velocities become v_{1} and v_{2}.  


Total momentum after collision = m_{1}v_{1} + m_{2}v_{2}  
According to the law of conservation of momentum  
m_{1}u_{1}
+ m_{2}u_{2} = m_{1}v_{1} + m_{2}v_{2}

