Here, mass of the body, $m=2\, kg$ and time,
$t=4\, s$
Impulse $=p_{f}-p_{i}$
where, $p_{i}=$ initial momentum,
$p_{f}=$ final momentum
Impulse $m v_{f}-m v_{i}=m\left(v_{f}-v_{i}\right)$
$(\because p=m v)$
As from the graph,
$v_{f}=\frac{3-3}{8-4}=0$ and $v_{i}=\frac{3-0}{4-0}=\frac{3}{4}$
Impulse $=2 \times\left(0-\frac{3}{4}\right)$
$=-1.5 \,kg = ms ^{-1}$
