Answer: c
Explanation:
Analytical methods 
        
             
        
        
        
Jogging side by side since the speed is equal and the direction is the same i.e same velocity
        
             
        
        
        
The center of mass is given with this formula:

Velocity is:

So, for the velocity of the center of mass we have:

In our case it is:
 
 
 
        
        
        
Explanation:
it is given that, the linear charge density of a charge, 
Firstly, we can define the electric field for a small element and then integrate for the whole. The very small electric field is given by :
 ..........(1)
..........(1)
The linear charge density is given by :


Integrating equation (1) from x = x₀ to x = infinity



Hence, this is the required solution.
 
        
                    
             
        
        
        
We know that momentum = mass times velocity 
So a. 720 kgm/s