The displacement $(x)$ and time $(t)$ graph of a particle moving along a straight line is shown in the figure. The average velocity of the particle in the time of $10 \ s$ is (in $m \ s^{-1}$)

$A$ car covers distance $AB$ with the first one-third at velocity $v_{1} \, ms^{-1}$,the second one-third at $v_{2} \, ms^{-1}$,and the last one-third at $v_{3} \, ms^{-1}$. If $v_{3}=3v_{1}$,$v_{2}=2v_{1}$,and $v_{1}=11 \, ms^{-1}$,then the average velocity of the car is . . . . . . $ms^{-1}$.

Velocity of an object in rectilinear motion is given as a function of time by $v = t - t^3$,where $v$ is in $m/s$ and $t$ is in seconds. Its average velocity over the time interval from $t = 0 \ s$ to $t = 2 \ s$ is ........ $m/s$.

$A$ car travels from $A$ to $B$ at a speed of $20\,km/hr$ and returns at a speed of $30\,km/hr$. The average speed of the car for the whole journey is............$km/hr$

$A$ person walks along a straight road from his house to a market $2.5 \,km$ away with a speed of $5 \,km/h$ and instantly turns back and reaches his house with a speed of $7.5 \,km/h$. The average speed of the person during the time interval $0$ to $50 \,min$ is (in $m/s$)

Write the relation between speed and the magnitude of velocity.