I have attached an image showing the diagram.
Answer:
-2 m/s²
Explanation:
From the diagram, in decelerating from between 60 to 70 seconds, it moved from a velocity of 20 m/s to 0 m/s.
Thus, using Newton's first equation of motion, we can find the deceleration;
a = (v - u)/t
Time (t) = 70 - 60 = 10 s
Final velocity (v) = 0 m/s
Initial velocity (u) = 20 m/s
Thus;
a = (0 - 20)/10
a = -20/10
a = -2 m/s²