$A$ bus decreases its speed from $80 \, km \, h^{-1}$ to $50 \, km \, h^{-1}$ in $4 \, s$. Find the acceleration of the bus.

State whether the following statement is true or false:
Velocity and speed are measured in different units.

What is the relationship between the distance travelled and the time elapsed for motion with uniform velocity?

$(a)$ Which type of motion is represented by the velocity-time graph shown below?
$(b)$ Name the physical quantity which can be calculated by the area of rectangle $OABC$.
$(c)$ What does the straight line $AB$ represent?

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?

State whether the following statement is true or false:
In one-dimensional motion,the average velocity and the instantaneous velocity are unequal.