$A$ cyclist goes once around a circular track of diameter $105 \, m$ in $5 \, minutes$. Calculate his speed. (in $m/s$)

What is the numerical ratio of average velocity to average speed of an object when it is moving along a straight path?

State whether the following statements are true or false:
$1$. The motion in animals is called locomotion.
$2$. Mechanics deals with the motion of non-living objects.

$A$ car manufacturer advertises that the brakes are so perfect that the car stops instantaneously. Comment.

An object starts a linear motion with velocity $u$ and with uniform acceleration $a$,it acquires a velocity $v$ in time $t$.
$(a)$ Draw its velocity-time graph.
$(b)$ Obtain the first equation of motion,$v = u + at$,for the velocity-time relation by using the velocity-time graph.
$(c)$ $A$ body moving with a velocity of $2 \, m s^{-1}$ acquires a velocity of $10 \, m s^{-1}$ in $5 \, s$. Find its acceleration.

Name a physical quantity that essentially changes as a body moves.