If two vectors going in opposite directions and we add them, the resultant is given by the sum of vectors as :
, cos (180) = -1
If the vectors are in same directions, the resultant is equal to the sum of vectors. Here, the resultant of two vectors is smaller because the part of the velocities cancel out each other. Hence, the correct option is (c).
You can use the impulse momentum theorem and just subtract the two momenta. P1 - P2 = (16-1.2)(11.5e4)=1702000Ns If you first worked out the force and integrated it over time the result is the same