Figure gives a speed-time graph of a particle in motion along a constant direction. Three equal intervals of time are shown. In which interval is the average acceleration greatest in magnitude ? In which interval is the average speed greatest ? Choosing the positive direction as the constant direction of motion, give the signs of $v$ and $a$ in the three intervals. What are the accelerations at the points $A, B, C$ and $D$?

One car moving on a straight road covers one third of the distance with $20 \,km/hr $ and the rest with $60\, km/hr$. The average speed is……….$km/hr$

A boy walks to his school at a distance of $6\, km$ with constant speed of $2.5\, km/hour $ and walks back with a constant speed of $4 \,km/hr.$ His average speed for round trip expressed in $km/hour$, is

A vehicle travels half the distance with speed $v$ and the remaining distance with speed $2\,v$.Its average speed is :

Define speed. Define average speed.