$A$ particle moves for $20 \,s$ with velocity $3 \,m/s$,then with velocity $4 \,m/s$ for another $20 \,s$,and finally with velocity $5 \,m/s$ for the next $20 \,s$. What is the average velocity of the particle in $m/s$?

$A$ car travels a distance $S$ on a straight road in two hours and then returns to the starting point in the next three hours. Its average velocity is

If a body covers one-third of its total distance at speed $v_1$,the next one-third at speed $v_2$,and the last one-third at speed $v_3$,then the average speed will be:

$A$ person goes from point $P$ to point $Q$ covering $1/3$ of the distance with speed $10 \, km/h$,the next $1/3$ of the distance at $20 \, km/h$,and the last $1/3$ of the distance at $60 \, km/h$. The average speed of the person is ............ $km/h$.

$A$ train travels from city-$A$ to city-$B$ with a constant speed of $18 \,ms^{-1}$ and returns back to city-$A$ with a constant speed of $36 \,ms^{-1}$. Find its average speed during the journey. (in $\,ms^{-1}$)

In $1.0 \, s$,a particle moves from point $A$ to point $B$ along a semicircle of radius $1.0 \, m$ (see figure). The magnitude of the average velocity is ......... $m/s$.