The figure shows the position-time graph of a body of mass 0.04 kg. Suggest a suitable physical context for this motion. What is the time between two consecutive impulses received by the body? What is the magnitude of each impulse? 

The graph could be representing a ball rebounding between two walls separated by 2 cm with a constant velocity in free space. After receiving the impulse ball changes its direction. Hence time between two impulses is 2 seconds. 
$velocity=\frac{displacement}{time}=\frac{2\times 10^{-2}}{2}=0.01m/s$
Initial momentum, 
$mu=0.04\times 10^{-2}kgm/s$ 
Final momentum, 
$mv=-0.04\times 10^{-2}kgm/s$ 
$\therefore$ Change in momentum = 0.08 \times 10^{-2} kgm/s $$