The following plots show variation of velocity $(v)$ with time $(t)$ of a ball thrown vertically upward, and falling back. Which of the following plots is/are correct?

When a ruler falls vertically, 5 different persons catch it with different reaction times. ( $g=9.8 \mathrm{~m} \mathrm{~s}^{-2}$ )

A. Person A has reaction time of 0.20 s .

B. Person $B$ has reaction time of 0.22 s .

C. Person C has reaction time of 0.18 s .

D. Person D has reaction time of 0.19 s .

E. Person E has reaction time of 0.21 s .

What is the correct order of the distance travelled by the ruler for each person?

In some appropriate units, time $(t)$ and position $(x)$ relation of a moving particle is given by $t=x^2+x$. The acceleration of the particle is

Two cities $X$ and $Y$ are connected by a regular bus service with a bus leaving in either direction every $T$ min. A girl is driving scooty with a speed of $60 \mathrm{~km} / \mathrm{h}$ in the direction $X$ to $Y$ notices that a bus goes past her every 30 minutes in the direction of her motion, and every 10 minutes in the opposite direction. Choose the correct option for the period $T$ of the bus service and the speed (assumed constant) of the buses.