Answer:
1.67 m/s²
Explanation:
Total force is;
ΣF = F_f + F_a
From the free body diagram attached, we see that the frictional force F_f is acting in a negative direction.
Thus;
ΣF = -15 + 30
ΣF = 15 N
Now, to get the acceleration, we will use the formula;
ΣF = ma
We are given m = 9 kg
Thus;
15 = 9a
a = 15/9
a = 1.67 m/s²