What does a vehicle's speedometer measure: instantaneous velocity or instantaneous speed?

The relation $3t = \sqrt{3x} + 6$ describes the displacement of a particle in one direction,where $x$ is in $m$ and $t$ is in $s$. The displacement,when velocity is zero,is ......... $m$.

The velocity-time graph for a car is a semicircle as shown in the figure. Which of the following statements is correct?

The velocity $v$ of a body moving along a straight line varies with time $t$ as $v = 2 t^2 e^{-t}$,where $v$ is in $m/s$ and $t$ is in $s$. The acceleration of the body is zero at $t =$

The position-time graphs for two students $A$ and $B$ returning from the school to their homes are shown in the figure.
$(A)$ $A$ lives closer to the school.
$(B)$ $B$ lives closer to the school.
$(C)$ $A$ takes less time to reach home.
$(D)$ $A$ travels faster than $B$.
$(E)$ $B$ travels faster than $A$.
Choose the correct answer from the options given below:

The acceleration versus velocity graph of a particle moving in a straight line,starting from rest,is as shown in the figure. The corresponding velocity-time graph would be: