Answer
The net force has a magnitude of $1725N$ and is directed due west.
Work Step by Step
1) Find the deceleration $a$ of the car
Initial velocity $v_0=27m/s$, final speed $v=17m/s$, duration $t=8s$
$$v=v_0+at$$ $$a=\frac{v-v_0}{8}=-1.25m/s^2$$
2) The car has mass $m=1380kg$. The net force that produces this deceleration is $$\sum F=m_{car}a=-1725N$$
- Magnitude: $\sum F=1725N$
- Direction: the negative sign indicates that $\sum F$ is directed opposite the direction of travel, so it is directed due west.
