Let the two balls A and B moving in opposite directions collide and rebound with same speed. Initial momentum of the ball A = 0.05 × (6) = 0.3 kg m s $^{-1}$ Final momentum of the ball A = 0.05(–6) = –0.3 kg m s$^{-1}$ Impulse imparted to ball A = change in momentum of ball $A=$ final momentum - initial momentum $=-0.3-0.3=-0.6 \text{kg} \text{m} \text{s}^{-1}$ Initial momentum of the ball $B=0.05 \times(-6)=-0.3 \text{kg} \text{m} \text{s}^{-1}$ Final momentum of the ball $B=0.05\times(6)=0.3 \text{kg} \text{m} \text{s}^{-1}$ Impulse imparted due to $B=0.3-(-0.3)=0.6 \text{kg} \text{m} \text{s}^{-1}$Impulse on each ball is 0.6 $\text{kg} \text{m} \text{s}^{-1}$ in magnitude but these two impulses are opposite in direction.