Question 4
On the same cycle journey, the child's displacement was 8 m at t = 8 s and 0 at t = 10 s.
What was the child's velocity during the last 2 seconds?
The right answer is the one marked above.
−4 m s-1. Velocity is the change in displacement divided by the time:
velocity = (0 − 8) m ÷ 2 s = −4 m s-1
The negative sign says the motion was in the direction opposite to the original one — that is, a velocity of 4 m s-1 back the way they came. Since the displacement is 0 at t = 10 s, the child has returned to the starting point.