$A$ train has a speed of $60\, km/h$ for the first one hour and $40\, km/h$ for the next half hour. Its average speed in $km/h$ is

Write the relation between speed and the magnitude of velocity.

$A$ bus travels the first one-third distance at a speed of $10\; km/h$,the next one-third at $20\; km/h$,and the last one-third at $60\; km/h$. The average speed of the bus is ........ $km/h$.

$A$ 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 $m/s$?

$A$ 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 in a straight line along a road. Its distance $x$ from a stop sign is given as a function of $t$ by the equation $x(t) = \alpha t + \beta t^3$,where $\alpha = 2.0 \ m \ s^{-1}$ and $\beta = 0.01 \ m \ s^{-3}$. Calculate the average velocity of the car in the time interval $t = 2.00 \ s$ to $t = 4.00 \ s$. (in $m \ s^{-1}$)