Is the statement "$A$ particle can have zero speed but non-zero velocity" true or false? Explain.

$A$ 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 $m/s$?

Why can the speed of a moving object never be negative?

$A$ biker travels $\frac{1}{3}$ of the distance $L$ with speed $v_1$ and $\frac{2}{3}$ of the distance with speed $v_2$. Then the average speed is

$A$ 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 of the man over the interval of time $0$ to $30 \; min$?

$A$ 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............$km/hr$