Area under speed$-$time graph is equal to the

A car travels $100\, km$ east and then $100 \,km$ south. Finally, it comes back to the starting point by the south-east route. Throughout the journey the speed is constant at $60\, km h ^{-1}$. The average velocity for the whole journey if time taken is $3.3$ hours is

A girl running a race accelerates at $2.5\, m s ^{-2}$ for the first $4\, s$ of the race. How far does she travel in this time ?

A body is moving, with a velocity of $10 \,m s ^{-1}$. If the motion is uniform, what will be its velocity after $10 \,s$ ?

Mention some uses of velocity$-$time graphs.