The velocity$-$time graph of a body has a negative slope. The body is undergoing

Why does $(second)^{2}$ occur in the unit of acceleration?

What is the nature of motion of a particle depicted by the following displacement-time graphs?

What does the odometer of an automobile measure? Which of the following is moving faster? Justify your answer.
$(i)$ $A$ scooter moving with a speed of $300 \, m$ per minute.
$(ii)$ $A$ car moving with a speed of $36 \, km$ per hour.

$A$ body can have zero average velocity but not zero average speed. Justify.

$(a)$ Derive graphically the equation for velocity$-$time relation.
$(b)$ Name the device used to measure distance travelled by a vehicle.
$(c)$ Can displacement of a moving object be zero? Give reason.