Answer
Acceleration = $\frac{final\, velocity - initial\, velocity}{time}$
So,
from 0 to 4.0 s, acceleration = $\frac{8-0}{4-0}=2 m/s^{2}$
from 4.0 to 10.0 s, acceleration = $\frac{8-8}{10-4}=0 m/s^{2}$
from 10.0 to 18.0 s, acceleration = $\frac{0-8}{18-10}=-1 m/s^{2}$
From 0 to 4.0 s, the object accelerates with $2 m/s^{2}$ to velocity of 8 m/s, then from 4.0 s to 10.0 s, it keeps a constant velocity of 8 m/s, then from 10.0 s to 18.0 s, it decelerates at $-1 m/s^{2}$ till it comes to rest.
Work Step by Step
Acceleration = $\frac{final\, velocity - initial\, velocity}{time}$
So,
from 0 to 4.0 s, acceleration = $\frac{8-0}{4-0}=2 m/s^{2}$
from 4.0 to 10.0 s, acceleration = $\frac{8-8}{10-4}=0 m/s^{2}$
from 10.0 to 18.0 s, acceleration = $\frac{0-8}{18-10}=-1 m/s^{2}$
From 0 to 4.0 s, the object accelerates with $2 m/s^{2}$ to velocity of 8 m/s, then from 4.0 s to 10.0 s, it keeps a constant velocity of 8 m/s, then from 10.0 s to 18.0 s, it decelerates at $-1 m/s^{2}$ till it comes to rest.
