The displacement $(x)$ - time $(t)$ graph of a particle is shown in the figure. Which of the following is correct?

The velocity $v$ of a particle is given by the equation $v = 6t^2 - 6t^3$,where $v$ is in $m/s$ and $t$ is time in $s$. Then:

Two small blocks slide without losing contact with the surface along two frictionless tracks $1$ and $2$,starting at the same time with the same initial speed $v$. Track $1$ is perfectly horizontal,while track $2$ has a dip in the middle,as shown in the figure. Which block reaches the finish line first? [Hint: Use velocity-time graph to solve]

Which of the following speed-time $(v-t)$ graphs is physically not possible?

The position-time $(x-t)$ graphs for two children $A$ and $B$ returning from their school $O$ to their homes $P$ and $Q$ respectively are shown in the figure. Choose the correct entries in the brackets below:
$(a)$ $(A/B)$ lives closer to the school than $(B/A)$
$(b)$ $(A/B)$ starts from the school earlier than $(B/A)$
$(c)$ $(A/B)$ walks faster than $(B/A)$
$(d)$ $A$ and $B$ reach home at the (same/different) time
$(e)$ $(A/B)$ overtakes $(B/A)$ on the road (once/twice)

The displacement-time graphs of two moving particles make angles of $30^{\circ}$ and $45^{\circ}$ with the time-axis as shown in the figure. The ratio of their respective velocities is: