If the average velocity of a body is equal to the mean of its initial velocity and final velocity,then the acceleration of the body is

Study the given velocity-time graph and answer the following questions:
$(i)$ Which part of the graph shows accelerated motion?
$(ii)$ Which part of the graph shows retarded motion?
$(iii)$ Calculate the distance travelled by the body in the first $4 \ s$ of the journey graphically.

$A$ piece of stone is thrown vertically upwards. It reaches its maximum height in $3 \ s$. If the acceleration of the stone is $9.8 \ m s^{-2}$ directed towards the ground,calculate the initial velocity of the stone with which it is thrown upwards. Find the maximum height attained by it.

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

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

Two stones are thrown vertically upwards simultaneously with their initial velocities $u_{1}$ and $u_{2}$ respectively. Prove that the heights reached by them would be in the ratio of $u_{1}^{2}: u_{2}^{2}$ (Assume upward acceleration is $-g$ and downward acceleration is $+g$).