Answer: Negative acceleration
Step-by-step explanation:
According to the described situation we have two velocities:
-An initial velocity during the first hour:
![V_(o)=400 mi/h](https://img.qammunity.org/2020/formulas/physics/middle-school/wzs8pwevlzodcdcesxz3sq93y2dka2l52u.png)
-A final velocity during the last 200 miles:
![V_(f)=200 mi/h](https://img.qammunity.org/2020/formulas/physics/middle-school/zry1dhowlkakzh4sok6pi8z1fkswbezwki.png)
As we can see, the final velocity is less than the initial velocity, this means the plane's velocity decreased.
On the other hand, acceleration
is defined as the variation of velocity in time:
Since the plane's velocity decreases, the acceleration is negative.
Hence, this situation is an example of negative acceleration.