To develop this problem it is necessary to use the concepts related to Impulse.
The impulse is defined as the change in velocity at the rate of mass, that is
[tex]L = m\Delta V,[/tex]
Where,
m = Mass
[tex]\Delta V =[/tex] Change in Velocity
This change in velocity can be expressed as,
[tex]L = m(v_2-v_1)[/tex]
[tex]L = 0.45*(12.8 - 3.2)[/tex]
[tex]L = 0.45*9.6[/tex]
[tex]L= 4.32 Kg.m/s[/tex]
Therefore the magnitude of the impulse is 4.32 Kg.m/s