Answer:
31 m/s south
Step-by-step explanation:
Since the acceleration, a, is to the south (opposite the initial direction of motion), the sign is negative (-).
Let north be + positive direction and south be - negative direction
a = (Vf - Vi) / Δt
a = - 3 m/s²
Vf = ?
Vi = 23 m/s north
- 3 m/s² = (Vf - 23 m/s) / 18 s solve for Vf
Vf = (- 3 m/s²)(18 s) + 23 m/s = -31 m/s meaning, it was going south