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

Explain the following type of motion with one example of each

$(i)$ Acceleration is positive

$(ii)$ Acceleration is negative

$(iii)$ Acceleration is zero.

A body moves with a velocity of $2\, m s ^{-1}$ for $5\, s$, then its velocity increases uniformly to $10\, m s ^{-1}$ in next $5\, s.$ Thereafter, its velocity begins to decrease at a uniform rate until it comes to rest after $5\, s$.

$(i)$ Plot a velocity-time graph for the motion of the body.

$(ii)$ From the graph, find the total distance covered by the body after $2\, s$ and $12\, s$.

Account for the following

$(a)$ Name the quantity which is measured by the area occupied below the velocity$-$time graph.

$(b)$ An object is moving in a certain direction with acceleration in the perpendicular directions.

$(c)$ Under what condition is the magnitude of average velocity of an object equal to its average speed ?

$(d)$ An example of uniformly accelerated motion.

$(e)$ A body is moving along a circular path of radius

$(r)$. What will be the distance and displacement of the body when it completes half revolution ?

Differentiate between distance and displacement.