Answer:
New Momentum of Ball B
<u>Explanation:</u>
Given:
Mass of Ball A=1kg
Mass of Ball B= 2kg
Mass of Ball C=5kg
Mass of Ball D=7kg
Velocities of A=B=C=D=2.2
Momentum of Ball A=2.2
Momentum of Ball B=4.4

Momentum of Ball C=11 
Momentum of Ball D=15 
To Find:
 Change in Momentum When of Ball B gets tripled
Solution:
Though all balls have same velocity, thus we get
Velocities of A=B=C=D=2.2
Initial Momentum of Ball B=4.4 
If the Mass of Ball B gets tripled;
We get New Mass of Ball B=3×Actual Mass of the ball
                                             =3×2=6kg
Thus we get Mass of Ball B=6kg
According to the formula,  
Change in momentum of Ball B  
Where  =change in momentum
=change in momentum
           m=mass of the ball B
           =change in velocity ball B
=change in velocity ball B
And  since all balls, have same velocity
 since all balls, have same velocity
Thus the above equation, changes to
          
Substitute all the values in the above equation we get
           
                       
  
Result:
  Thus the New Momentum of ball B