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

$A$ truck is moving on a straight road with uniform acceleration. The following table gives the speed of the truck at various instants of time.

Speed $(m s^{-1})$	$5$	$10$	$15$	$20$	$25$	$30$
Time $(s)$	$0$	$10$	$20$	$30$	$40$	$50$

Draw the speed-time graph by choosing a convenient scale. Determine from it:
$(i)$ The acceleration of the truck.
$(ii)$ The distance travelled by the truck in $50$ seconds.

The velocity$-$time graph of an ascending passenger lift is as shown in the figure below.
$(i)$ Identify the kind of motion of the lift represented by lines $OA$ and $BC$.
$(ii)$ Calculate the acceleration of the lift:
$(a)$ During the first two seconds.
$(b)$ Between the $3^{rd}$ and $10^{th}$ second.
$(c)$ During the last two seconds.

The area under a $v-t$ graph represents a physical quantity which has the unit:

By giving an example,prove that rest and motion are relative terms.

The speed-time graphs of two cars are represented by $P$ and $Q$ as shown below.
$(a)$ Find the difference in the distance travelled by the two cars (in $m$) after $4\, s$.
$(b)$ Do they ever move with the same speed? If so,when?
$(c)$ What type of motion are car $P$ and car $Q$ undergoing?