The average acceleration is -5.0 m·s⁻².
The formula for acceleration (a) is
[tex]a = \frac{v_{f}- v_{i}}{t}[/tex]
[tex]v_{f}[/tex] = 25 m·s⁻¹; [tex]v_{i}[/tex] = 0; [tex]t[/tex] = 5.0 s
∴ [tex]a = \frac{0-25}{5.0}[/tex] = -5.0 m·s⁻²
The negative sign tells you that the object is slowing down, i.e., it is decelerating.
