Centre of Mass and Collision Part 1

Motion is uniform as graph is straight line. In x-t graph, velocity is ‌

x

t

and the slope of the graph tells the direction of the velocity. Here because of impulse the direction of velocity or slope of the graph changes.
During each collision
Initial velocity v1=‌

2

2

=1ms−1
Final velocity v2=−‌

2

2

=−1ms−1
Impulse = Change in momentum
=m|v2−v1

‌

‌

|=0.4×2=0.8‌Ns