Why instantaneous velocity is defined ?

A particle moves along a straight line such that its displacement at any time $t$ is given by $s = {t^3} – 6{t^2} + 3t + 4$ metres. The velocity when the acceleration is zero is……..$m{s^{ – 1}}$

$A$ hinged construction consists of three rhombs with the ratio of sides $5:3:2$. Vertex $A_3$ moves in the horizontal direction at a velocity $v$. Velocity of $A_2$ is ……. $V$.

A woman starts from her home at $9.00\; \mathrm{am}$, walks with a speed of $5\; \mathrm{km} h^{-1}$ on a straight road up to her office $2.5\; \mathrm{km}$ away, stays at the office up to $5.00 \;\mathrm{pm}$, and returns home by an auto with a speed of $25\; \mathrm{km} h^{-1}$. Choose suitable scales and plot the $x -t$ graph of her motion