$A$ metro train starts from rest and in $5 \, s$ achieves $108 \, km/h$. After that,it moves with constant velocity and comes to rest after travelling $45 \, m$ with uniform retardation. If the total distance travelled is $395 \, m$,then the total time of travelling is ....... $s$.

An aircraft is flying at a height of $3400 \; m$ above the ground. If the angle subtended at a ground observation point by the aircraft positions $10.0 \; s$ apart is $30^{\circ}$,what is the speed in $m/s$ of the aircraft?

Statement $(I)$: An object subjected to velocities $\overrightarrow{v_1}$ and $\overrightarrow{v_2}$ has a resultant velocity with magnitude $|\vec{v}| = |\overrightarrow{v_1}| + |\overrightarrow{v_2}|$.
Statement $(II)$: The magnitude of displacement is either less than or equal to the path length of an object between two points.
Statement $(III)$: The instantaneous acceleration is the limiting value of the average acceleration as the time interval approaches zero.
Which of the following is correct?

For any arbitrary motion in space,which of the following relations are true?
$(a)$ $v_{\text{average}} = (1/2) (v(t_1) + v(t_2))$
$(b)$ $v_{\text{average}} = [r(t_2) - r(t_1)] / (t_2 - t_1)$
$(c)$ $v(t) = v(0) + at$
$(d)$ $r(t) = r(0) + v(0)t + (1/2)at^2$
$(e)$ $a_{\text{average}} = [v(t_2) - v(t_1)] / (t_2 - t_1)$
(The 'average' stands for the average of the quantity over the time interval $t_1$ to $t_2$.)

In the $s-t$ equation $(s=10+20t-5t^2)$,match the following columns.

Column $I$	Column $II$
$(A)$ Distance travelled in $3\,s$	$(p)$ $-20$ units
$(B)$ Displacement in $1\,s$	$(q)$ $15$ units
$(C)$ Initial acceleration	$(r)$ $25$ units
$(D)$ Velocity at $4\,s$	$(s)$ $-10$ units

Let $v$ and $a$ denote the velocity and acceleration respectively of a body. Which of the following statements is correct?