Answer:
-4.0 m/s^2
Step-by-step explanation:
Acceleration is defined as the rate of change in velocity:
![a=(v-u)/(t)](https://img.qammunity.org/2020/formulas/physics/middle-school/rbz9i28f98a6dvpx0ghax9pxq7qjfdf5sd.png)
where
v is the final velocity
u is the final velocity
t is the time elapsed
For the object in this problem,
u = 65 m/s
v = 25 m/s
t = 10 s
So the acceleration is
![a=(25 m/s-65 m/s)/(10 s)=-4.0 m/s^2](https://img.qammunity.org/2020/formulas/physics/middle-school/rp6nu2yhvo8lsb52lstojkaz9kbuahrcjv.png)
The negative sign tells that the acceleration is opposite (=west) to the velocity (which is towards east).