Answer
$\Delta p=4.05 \space Kg.m/s$
Work Step by Step
The change in the momentum of the bullet can be determined as follows:
$\Delta p=m\Delta v$
$\implies \Delta p=m(v_f-v_i)$
We plug in the known values to obtain:
$\Delta p=0.015(120-(-150))$ (The negative sign with initial value indicates the opposite direction)
This simplifies to:
$\Delta p=4.05 \space Kg.m/s$
