Answer:
The train's acceleration is positive (in the first part)
The train's acceleration is negative. (in the second part)
Explanation:
The acceleration of an object is given by:
[tex]a=\frac{v-u}{t}[/tex]
where v is the final velocity, u is the initial velocity, t is the time taken.
In the first part, the train accelerates from u = 10 m/s to v = 25 m/s in t =240 s, so the acceleration is
[tex]a=\frac{25 m/s-10 m/s}{240 s}=0.063 m/s^2[/tex]
and the sign is positive since the speed of the train is increasing.
In the second part, the train decelerates from u = 25 m/s to v = 0 (it comes to rest), in a time of t = 6 min = 360 s, so the acceleration is
[tex]a=\frac{0 m/s-25 m/s}{360 s}=-0.069 m/s^2[/tex]
and the sign is negative, since the speed of the train is decreasing.
