How can you find the distance travelled by a body in uniform motion from the velocity$-$time graph?

The velocity-time graph of a truck is plotted below.
$(a)$ Calculate the magnitude of displacement of the truck in $15$ seconds.
$(b)$ During which part of the journey was the truck decelerating?
$(c)$ Calculate the magnitude of average velocity of the truck.

Differentiate between distance and displacement.

$A$ cheetah can accelerate from rest at the rate of $4 \, m \, s^{-2}$.
$(i)$ What will be the velocity attained by it in $10 \, s$?
$(ii)$ How far will it travel in this duration?

$(a)$ $A$ car moving with uniform velocity $u$ and uniform acceleration $a$ covers a distance $S$ in time $t$. Draw its velocity-time graph and derive an expression relating all the given physical quantities.
$(b)$ $A$ boy revolves a stone tied to a string $0.7 \, m$ long. Find the distance and displacement covered by the stone in completing two revolutions from the starting point.

$(a)$ Which type of motion is represented by the velocity-time graph shown below?
$(b)$ Name the physical quantity which can be calculated by the area of rectangle $OABC$.
$(c)$ What does the straight line $AB$ represent?