Under what condition will the displacement and distance have the same magnitude?

In a long distance race,the athletes were expected to take four rounds of the track such that the finish line was the same as the start line. Suppose the length of the track was $200 \ m$.
$(a)$ What is the total distance to be covered by the athletes?
$(b)$ What is the displacement of the athletes when they touch the finish line?
$(c)$ Is the motion of the athletes uniform or nonuniform?
$(d)$ Is the displacement of an athlete and the distance moved by him at the end of the race equal?

$(a)$ Define uniform circular motion.
$(b)$ Is the uniform circular motion an accelerated motion? Give reasons for your answer.

$A$ driver of a train travelling at $40 \, m s^{-1}$ applies the brakes as the train enters a station. The train slows down at a rate of $2 \, m s^{-2}$. The platform is $400 \, m$ long. Will the train stop in time?

The velocity-time graph of a body is as shown. What type of motion does the body possess?

Ali,while driving to school,computes the average speed for his trip to be $20 \, km \, h^{-1}$. On his return trip along the same route,there is less traffic and the average speed is $30 \, km \, h^{-1}$. What is the average speed for Ali's entire trip?