Distinguish between the terms speed and velocity.

Abdul,while driving to school,computes the average speed for his trip to be $20 \, km \, h^{-1}$. On his return trip along the same route,there is less traffic and the average speed is $40 \, km \, h^{-1}$. What is the average speed (in $km \, h^{-1}$) for Abdul's trip?

$A$ train $100 \, m$ long is moving with a velocity of $60 \, km/h$. Find the time it takes to cross a bridge $1 \, km$ long.

The momentum of a body of given mass is proportional to its

The average time taken by a normal person to react to an emergency is $1/15$ of a second and is called the 'reaction time'. If a bus is moving with a velocity of $60 \, km/h$ and its driver sees a child running across the road,how much distance would the bus have moved before he could press the brakes? The reaction time of the people increases when they are intoxicated. How much distance would the bus have moved if the reaction time of the driver were $1/2 \, s$ under the influence of alcohol?

Ali,while driving to school,computes the average speed for his trip to be $20 \, km \, h^{-1}$. On his return trip along the same route,there is less traffic and the average speed is $30 \, km \, h^{-1}$. What is the average speed for Ali's entire trip?