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

$A$ body is thrown vertically upward with velocity $u$,the greatest height $h$ to which it will rise is,

$(a)$ Differentiate between distance and displacement.
$(b)$ Under what conditions is the magnitude of average velocity of an object equal to its average speed?

$A$ girl of mass $50\, kg$ jumps out of a moving boat of mass $300\, kg$ on to the bank with a horizontal velocity of $3\, m s^{-1}$. With what velocity does the boat begin to move backwards (in $, m s^{-1}$)?

Velocity-time graph for the motion of an object in a straight path is a straight line parallel to the time axis.
$(a)$ Identify the nature of motion of the body.
$(b)$ Find the acceleration of the body.
$(c)$ Draw the shape of distance-time graph for this type of motion.

The diagram shows a velocity-time graph for a car starting from rest. The graph has three sections $AB$,$BC$,and $CD$.
$(i)$ From a study of this graph,state how the distance travelled in any section is determined.
$(ii)$ Compare the distance travelled in section $BC$ with the distance travelled in section $AB$.
$(iii)$ In which section does the car have zero acceleration?
$(iv)$ Is the magnitude of acceleration higher or lower than that of retardation? Give a reason.