The variation of velocity of a particle with time moving along a straight line is illustrated in the following figure. The distance travelled by the particle in $4 \; s$ is ......... $m$.

The position $x$ of a particle with respect to time $t$ along the $x$-axis is given by $x = 9t^2 - t^3$,where $x$ is in metres and $t$ is in seconds. What will be the position of this particle when it achieves maximum speed along the $x$-direction?

The displacement-time graph of a moving particle is shown below. The instantaneous velocity of the particle is negative at the point:

Refer to the graph in the figure. Match the following:

Let us define a motion as $A$ when velocity is positive and increasing,$A^{-1}$ when velocity is negative and increasing,$R$ when velocity is positive and decreasing,and $R^{-1}$ when velocity is negative and decreasing. Now,match the following two columns for the given $s-t$ graph.

Column $I$	Column $II$
$(A)$ $M$	$(p)$ $A^{-1}$
$(B)$ $N$	$(q)$ $R^{-1}$
$(C)$ $P$	$(r)$ $A$
$(D)$ $Q$	$(s)$ $R$

The instantaneous velocity of a body can be measured by: