Meaning of momentum
•mathematically momentum is product of mass and velocity
 that is   
Momentum=mass×velocity
Where 'm' mass of any object &
'V' is velocity of object
The two body named 'A' and 'B' of different mases m1&m2 and velocity v1 & v2 respectively. Then their momentum is constant i.e 
       mv=constant

When two bodies of whatever shape and size their momentum is same.