Explain the following type of motion with one example of each

$(i)$ Acceleration is positive

$(ii)$ Acceleration is negative

$(iii)$ Acceleration is zero.

A body is thrown vertically upward with velocity $u$, the greatest height $h$ to which it will rise is,

Account for the following

$(a)$ What is the shape of the path of a body when it is in uniform motion ?

$(b)$ Give one example of non$-$uniform motion.

$(c)$ Two cars $A$ and $B$ have their $x-t$ graph as shown in figure. Which has greater velocity ?

$(d)$ What is the quantity which is measured by the area occupied below the velocity$-$time graph ?

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

What is meant by free fall ? Two bodies, one of mass $1\,g$ and other of mass $1\, kg$ are dropped from the same height in vacuum. Compare the two time intervals in which the two bodies will hit the ground.

Give an expression for the speed of an athlete if he takes time $'t^{\prime}$ to go around a circular track, of radius ${ }^{\prime} r^{\prime}$