The adjacent figure shows the position graph of one dimensional motion of a particle of mass 4kg. The impulse at t=0 and t=4s is given respectively as:

t<0,vi=0 and t>0,vf=34 m/s∴ Impulse =m(vf−vi)=4(34−0)=3 kg ms−1 Little before 4 second v=34 m/s, little after 4 second,  velocity becomes zero . Therefore, Impulse =m(vf−vi)=4(0−34)=−3 kg ms−1