$A$ car moves from $A$ to $B$ with a speed of $30 \ km/h$ and from $B$ to $A$ with a speed of $20 \ km/h$. What is the average speed of the car (in $km/h$)?

$A$ man walks on a straight road from his home to a market $2.5 \; km$ away with a speed of $5 \; km \; h^{-1}$. Finding the market closed,he instantly turns and walks back home with a speed of $7.5 \; km \; h^{-1}$. What is the average speed (in $km/h$) of the man over the interval of time $0$ to $50 \; min$?

$A$ 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 ............ $km/h$.

$A$ car covers $2/5^{th}$ of the total distance with speed $v_1$ and $3/5^{th}$ of the total distance with speed $v_2$. What is its average speed?

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 ........ $m/s$.

$A$ particle moves along a semicircle of radius $10\,m$ in $5$ seconds. The average velocity of the particle is...........$m/s$.